Op/Ed: Recognizing Mass Shooters And Potential Attacks In Public Places, Federal Research


Recognizing Mass Shooters And Potential Attacks In Public Places, Federal Research. The following article has been written by Leonard Adam Sipes, Jr. It includes editorial content which is the opinion and story of the writer.


An overview of two recent documents on mass shootings and mass shooters from the US Secret Service and the National Institute of Justice.

Both contain the best summations of mass shooters and mass shootings. The recommended solutions may not be what you are expecting.


Leonard Adam Sipes, Jr.

Retired federal senior spokesperson. Thirty-five years of directing award-winning public relations for national and state criminal justice agencies. Interviewed multiple times by every national news outlet. Former Senior Specialist for Crime Prevention for the Department of Justice’s clearinghouse. Former Director of Information Services, National Crime Prevention Council. Former Adjunct Associate Professor of criminology and public affairs-University of Maryland, University College. Former advisor to presidential and gubernatorial campaigns. Former advisor to the “McGruff-Take a Bite Out of Crime” national media campaign. Certificate of Advanced Study-Johns Hopkins University. Former police officer. Aspiring drummer.

Author of ”Success With The Media: Everything You Need To Survive Reporters and Your Organization” available at Amazon and additional booksellers.

Predicting School Violence, Mass Shooters and Violent Crime

Quotes-Nashville Mass Shooting-USA Today

“They’re out there right now. They’re begging for us to do something,” Freeman said.

“We’re not going to fix it,” U.S. Rep. Tim Burchett, R-Tenn., told reporters Monday. “Criminals are going to be criminals.”


Because of recent mass shootings, people are asking if there is data on the offenders and what they did to carry out their attacks and methods to stop them.

Below are summations of two documents, one from the US Secret Service and one from the National Institute of Justice. Both are recent and both provide insights into mass shooters and the crimes they committed based on hundreds of research projects.

There is immense complexity in the findings. The combined documents seem to suggest that it’s up to communities, family, and friends to forward information to law enforcement indicating that a person is contemplating a mass shooting or has the characteristics of a mass shooter.

Complex Solutions

There are massive entanglements as to firearm control or mental health or social media bans as solutions.

There are approximately 400 million firearms in the private hands of Americans. If the overwhelming majority of mass shooters use handguns or if shooters can easily switch to high-powered hunting rifles or simply buy multiple clips, society is limited as to firearm bans or restrictions. Courts seem to overturn firearm restrictions on a constitutional basis weekly.

A very small percentage of shooters have a history of involuntary commitments as being a danger to themselves or others, the legal basis for denying the purchase of firearms. The costs of effectively treating 10 million Americans for mental health issues may be prohibitive.

As for social media, we can ban TikTok for running dangerous videos but other social media platforms will take their place.

This leaves us with bringing information to the authorities for an assessment as the only viable option which creates its own problems with privacy. In this day and age of thousands of police officers quitting, is law enforcement sufficiently staffed and trained to correctly analyze and respond to an increase in citizen tips? We are already running into problems enforcing red-flag laws. Does anyone understand the person power requirements to go to the home of a mentally ill person to remove firearms?

Much of what you will read below suggests that mass shooters and everyday violent criminals have much in common which makes identifying mass shooters very difficult.

You will find that there are multiple interpretations as to what constitutes a mass shooting and whether they include street-level criminality involving people the assailant knows or just those involving strangers as victims (i.e., a public mass shooting).

What is known is that without the public’s support in providing critical information (i.e., the potential shooter is telling others of what his plans are and is making final arrangements like giving away prized possessions) there is little law enforcement can constitutionally do.

There is guidance in the reports below advising law enforcement and others as to how to evaluate a potential shooter.

My question is whether society has it has its priorities correct. As horrifying and destructive as “public” mass shootings are, they remain a tiny percentage of homicides. Most murder and shooting victims are urban minorities that do not evoke nearly the reaction as public mass shootings. Why?

Editor’s note: I use italics throughout the two documents to focus on key points. I use reordered paragraphs for both federal documents.

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US Secret Service-2023

Behavioral threat assessment is a proactive approach pioneered by the U.S. Secret Service to prevent acts of targeted violence, including mass violence in communities across the United States.

This report builds upon a 25-year history of targeted violence research from the U.S. Secret Service̓s National Threat Assessment Center (NTAC) and demonstrates how mass attackers display a range of observable concerning behaviors across a variety of community systems as they escalate toward violence.

In short, NTAC’s examination of the attacks contained in this report indicates that targeted violence is preventable when communities are equipped with the appropriate tools, training, and resources to intervene before violence occurs.

Behavioral threat assessment programs are critical components of these community violence prevention efforts. These programs are not designed to predict who will become violent, but rather to identify, assess, and intervene with individuals who display threatening or other concerning behaviors that indicate they may pose a risk of harm to themselves or others.

As law enforcement agencies, workplaces, and other community organizations implement behavioral threat assessment programs, the approach should be guided by the research findings contained in this report.

When conducted properly, a behavioral threat assessment will involve promoting bystander reporting to identify warning signs of potential violence, systematically gathering information about the circumstances and behaviors of concern, assessing the possibility of violence as an outcome, and implementing preventive management strategies to make positive and safe outcomes more likely.

The 173 attacks contained in this report impacted a variety of locations, including businesses/workplaces, schools, houses of worship, military bases, nonprofit service providers, residential complexes, public transportation, and open spaces. In many cases, the attacker had a known affiliation with the site of the attack.

The analysis is intended to provide critical information to a cross-sector of community organizations that have a role in preventing these types of tragedies.

Key Findings Include

Most of the attackers had exhibited behavior that elicited concern in family members, friends, neighbors, classmates, co-workers, and others, and in many cases, those individuals feared for the safety of themselves or others.

Many attackers had a history of physically aggressive or intimidating behaviors, evidenced by prior violent criminal arrests/charges, domestic violence, or other acts of violence toward others.

Half of the attackers were motivated by grievances and were retaliating for perceived wrongs related to personal, domestic, or workplace issues.

Most of the attackers used firearms, and many of those firearms were possessed illegally at the time of the attack.

One-quarter of the attackers subscribed to a belief system involving conspiracies or hateful ideologies, including anti-government, anti-Semitic, and misogynistic views.

Many attackers experienced stressful events across various life domains, including family/romantic relationships, personal issues, employment, and legal issues. In some of these cases, attackers experienced a specific triggering event prior to perpetrating the attack.

Over half of the attackers experienced mental health symptoms prior to or at the time of their attacks, including depression, psychotic symptoms, and suicidal thoughts.

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Many of the pre-attack behaviors described in this report are not suspicious on their own, and some involve constitutionally protected activity.

Most individuals who exhibit these types of behaviors will not commit acts of targeted violence. NTAC’s research continues to affirm that there is no profile for the type of person who will commit an attack.

The U.S. Secret Service recognizes behavioral threat assessment as the best practice for targeted violence prevention because it does not utilize profiles, but focuses on identifying and assessing threatening and concerning behavior in context, and identifying the most appropriate strategies for reducing any risk of violence, while also maintaining individual civil and constitutional rights.

Based on this study examining mass attacks in public spaces from 2016 to 2020, and building on NTAC’s extensive history of studying all forms of targeted violence, the following operational implications are presented in support of developing policies and protocols for behavioral threat assessment programs.

Key Implications

Communities must encourage and facilitate bystander reporting and be prepared to respond when reports of concern are received. Three-quarters of the attackers exhibited concerning behaviors and communications.

Those who observed these behaviors had varying degrees of association with the attacker. They included family members, friends, neighbors, co-workers, school staff, mental health professionals, and local officials, as well as members of the public, both online and in person.

The breadth of people who observed these behaviors highlights the necessity of bystander reporting and behavioral threat assessment programs to assess and manage the risk posed by those individuals. Communities have made great strides in facilitating and encouraging bystander reporting of concerning behavior, and many environments have adopted behavioral threat assessment programs as part of their safety approach, including workplaces, schools, universities, government agencies, and police departments.

These organizations should continue to promote open and receptive communication between themselves and the public, ensuring that bystanders know what, when, and how to report behavior that elicits concerns for safety.

Communities should not wait for a direct and specific threat before taking action. While many attackers made direct or indirect threats prior to their attacks, the statements often lacked specificity.

Of those who made threats against the person or group they ultimately targeted, few specified where or when the attack would take place.

This demonstrates why waiting for an explicit threat that names the target, location, and timing of an intended attack will result in missed opportunities to prevent violence.

Such specificity, something that is often thought of as required to justify a response, should not be viewed as a threshold for taking preventive action when other warning signs of violence are present.

Early intervention is key to prevention and can be accomplished using existing community resources, including crisis intervention programs, social services, mental health treatment, and, if warranted, a criminal justice response.

Individuals displaying an unusual interest in violent topics, especially past attackers, should elicit concern. One-fifth of attackers had an excessive, inappropriate, or concerning interest in a violent topic, evidenced by such behaviors as repeatedly viewing footage of be-headings, writing and recording songs with violent themes, posting online about previous attacks, and keeping a journal about wanting to physically harm others.

As part of their planning, seven attackers conducted research specifically into prior mass attacks, including the Sandy Hook Elementary School shooting, the Oklahoma City bombing, the Marjory Stoneman Douglas High School shooting, and the Christchurch mosque shootings in New Zealand.

This is consistent with prior NTAC findings from Protecting America’s Schools: A U.S. Secret Service Analysis of Targeted School Violence (2019), which found that half of K-12 school attackers from 2008 to 2017 had displayed an unusual or concerning interest in violent topics, including the Columbine High School shooting and Nazism.

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Public safety professionals should recognize an unusual interest in violent topics as worthy of concern, especially an interest in previous mass attackers.

Businesses should consider establishing workplace violence prevention plans to identify, assess, and intervene with current employees, former employees, and customers who may pose a risk of violence.

In this study, half of the attacks involved one or more business locations and the attackers often had a prior relationship with the business, either as a current or former employee or as a customer.

What’s more, some in this study were motivated in whole or in part by a workplace grievance.

Workplaces should establish behavioral threat assessment programs as a component of their workplace violence prevention plans, and businesses should also establish proactive relationships with area law enforcement so that they may work collaboratively to respond to incidents involving a concern for violence, whether that concern arises from a current employee, a former employee, or a customer.

Public safety, school, workplace, and community service professionals should consider strategies for resolving interpersonal grievances. In this study, attackers displayed a range of motives for carrying out acts of violence, and in half of the incidents, attackers were motivated by some type of grievance.

These grievances were most often related to a personal issue, such as bullying, ongoing feuds with neighbors, or issues with family members.

In other attacks, grievances were related to a current or former domestic relationship or workplace issues. By understanding an individual’s motive to perpetrate a violent act, public safety and other professionals will be better equipped to employ management strategies and resources that will help de-escalate situations involving interpersonal conflicts.

Individuals tasked with community violence prevention must understand the impact of violent and hateful rhetoric while protecting the constitutional right to free speech.

One-quarter of the attackers in this study subscribed to a hate-focused, conspiratorial, or topic-specific belief system.

These beliefs were often directed toward a protected class, with biases expressed against others based on race, religion, national origin, sexual orientation, gender, and gender identity.

Hate-based beliefs included Anti-Semitism, anti-immigrant, anti-LGBTQ+, anti-Asian, anti-White, misogyny, and race-based supremacy.

Other beliefs involved anti-government and anti-police views. Government agencies and community organizations should continue directing resources, training, and public messaging toward countering hate and other extremist belief systems that have historically been associated with violence.

Misogyny and domestic violence deserve increased attention from those tasked with mass violence prevention. Nearly half of the attackers were found to have had a history of domestic violence, misogynistic behaviors, or both.

Though not all who possess misogynistic views are violent, viewpoints that describe women as the enemy or call for violence against women remain a cause for concern.

Nearly all of those who displayed misogynistic behaviors were found to have concerned others at some point prior to their attacks. These findings, along with those highlighted in NTAC’s case study, Hot Yoga Tallahassee: A Case Study on Misogynistic Extremism (2022), illustrate that misogyny can play a central role in motivating an attacker to perpetrate mass violence, as well as engage in more prevalent acts of violence, including stalking and domestic abuse.

No matter the context, responding to the threat posed by hatred toward women requires collaboration across multiple community systems, including law enforcement, courts, mental health providers, and domestic violence and hate crime advocacy groups.

Why I Always Kiss Him Goodbye

Online platforms may be utilized by individuals to make violent communications and to share violent rhetoric and ideas. The Internet allows individuals to come together and share common interests across online platforms and communities; however, these online communities can provide a place for violent and concerning ideas to manifest.

Nearly one-quarter of attackers were found to have conveyed concerning communications online, such as threats to harm others and posts referencing suicidal ideations, previous mass shootings, violent content, and hate toward a particular ethnic group.

One attacker was a member of an online chat group where members discussed plans to carry out school attacks. The attacker told the group that he planned to kill his father and that he would initiate a school attack the next day, which he did.

Another attacker had subscribed to anonymous radical online image boards over a year prior to his attack, and he later told officers this was when he started to adopt hatred toward Jewish people.

These findings demonstrate the continued need for encouraging the public to report concerning, threatening, and violent content observed across online platforms.

Individuals sharing final communications or engaging in other final acts may warrant immediate intervention. Behavioral threat assessment is a means for early identification and intervention to prevent targeted violence long before an act of violence could occur.

However, some individuals may come to attention only when violence appears imminent, by sharing final communications or engaging in acts that indicate an attack is fast approaching. Public safety professionals should understand these behaviors so they are able to recognize and intervene quickly and appropriately when a person is nearing violence.

Nearly one-quarter of attackers shared final communications before their attack, including calling people to say goodbye, authoring suicide notes, and posting manifestos online. Thirteen attackers made communications indicating that an attack was imminent, including one attacker who posted a photo of a gun online and sent a text message to a friend saying “it begins” minutes before initiating his attack.

Further, 18 attackers engaged in final acts, such as selling or giving away their personal possessions, canceling a cable subscription, and transferring ownership of a home to family members.

Community violence prevention efforts require identifying and promoting appropriate resources for individuals who are managing stressful life circumstances, experiencing mental health issues, or facing a personal crisis.

Nearly all attackers experienced at least one significant personal stressor in their lives within five years of the attack, and for most the stressors occurred within one year.

Stressors experienced by the attackers were most often related to things like financial instability, family issues, romantic relationships, court proceedings, employment, personal health issues, victimization, and homelessness.

Further, over half of the attackers experienced mental health symptoms prior to or at the time of their attacks, with many experiencing symptoms of multiple types of mental health disorders. The most common symptoms included depression, psychotic symptoms, and suicidal thoughts.

Those tasked with violence prevention will often encounter individuals requiring crisis intervention, as well as community resources and support to overcome challenging circumstances.

Communities should make available a variety of mental health and social services for those experiencing such challenges.

Mass shootings have been perpetrated by those who were legally prohibited from possessing firearms.

One-third of attackers in this study were prohibited by federal law from purchasing or possessing a firearm, including those with a prior felony or domestic violence conviction, fugitives from justice, those previously adjudicated incompetent or involuntarily committed to a mental health institution, and those who were currently the subject of a domestic-related protection order.

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Despite these prohibitions, 38 of these attackers used firearms during their attacks, including those that were acquired through straw purchases, theft, purchases from private sellers, and purchasing parts online.

Government agencies, courts, and law enforcement all have a role to play in ensuring weapons are not accessed by those individuals who are legally prohibited from gun ownership.

Local communities may have additional avenues for keeping weapons out of the hands of individuals at risk of causing harm. For example, some states have passed laws establishing extreme risk protection orders, sometimes referred to as “red flag laws.” These state laws maintain due process and protect the rights of gun owners, while also allowing for the temporary court-ordered removal of firearms from a person who poses an articulable risk of hurting other people or themselves.


US Secret Service

National Institute Of Justice-Mass Shootings-2022

The data below comes from the National Institute of Justice of the US Department of Justice and the Rand Corporation (one of the best crime-related research organizations in the nation) summarizing what we know and don’t know about mass shootings. What’s below is from that document. It’s a tool kit for understanding “and” responding to mass shootings.

Most will be a bit frustrated by the lack of clarity as to what constitutes a mass shooting, who commits them, their mental health issues, and what can be done. Those in law enforcement are exasperated by the national call for cops to be guardians, not warriors which seems wildly misplaced because law enforcement is expected to enter a mass shooting and stop the shooter, which requires endless tactical training and equipment.

In an earlier article, I point out that the great majority of what we call gun violence is street-level violent crime, not mass shooters. I suggest that the explosion of media coverage of mass shootings is somewhat misplaced; the vast majority of victims of gun violence are people of color and society has become immune to that violence.

It’s also important to point out that the overwhelming majority of mass shootings (77 percent) involve handguns, not assault weapons per another research project from the National Institute of Justice. You are going to discover some differences in this document (and others) versus the current Rand Corporation research. For example, 40 percent (below) broadcasted their shooting intentions versus 48 percent in previous research.

Yet what’s below is useful-necessary as to understanding the issues and being ready for a response.

Who Commits Mass Shootings?

According to this literature, the perpetrators of mass public shootings in the United States have been overwhelmingly male (98 percent) and are most commonly non-Hispanic White (61 percent). In addition, they are most commonly younger than age 45 (82 percent); more specifically, 26 percent of mass public shooters from 1976 to 2018 were younger than age 25, 27 percent were aged 25 to 34, and 29 percent were aged 35 to 44.

Relative to the overall U.S. population, mass public shooting offenders are much more likely to be male and are somewhat younger; relative to other homicide offenders, males and non-Hispanic Whites are over represented among mass public shooters, and mass public shooters are older.

For comparison, of the overall U.S. population in 2019, approximately 49 percent was male, 60 percent was younger than age 45, and 60 percent was non-Hispanic White (U.S. Census Bureau, 2020).

Of murderers in 2018 with known offender characteristics, 88 percent were men, 84 percent were younger than age 45 (38 percent younger than 25, 31 percent aged 25 to 34, and 16 percent aged 35 to 44), and 42 percent were White (Hispanic ethnicity information was not provided), (FBI, 2019).

Even if we did have definitive and complete data sources on the characteristics of all mass shooting incidents, it is still likely to be exceedingly difficult to identify useful predictors of mass shootings. With the exception of male sex, risk factors that appear to be over represented among mass shooters relative to the general population are often still uncommon among offenders on an absolute level.

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Thus, even if one could find a way to prevent individuals with a documented serious mental illness from committing a mass shooting—for example, developing and delivering effective treatments to more than 10 million Americans or effectively preventing their access to firearms—most mass shootings would still occur because only a fraction of mass shootings are committed by individuals with a documented history of serious mental illness.

Mental Health And Mass Shootings

Media coverage often links mass public shootings with serious mental illness, but estimates of the prevalence of mental illness among mass public shooting offenders vary widely depending on the types of incidents considered and the methods used to define and identify mental illness. Rates of formal diagnoses of psychotic disorders (including diagnoses made post-incident, which may be affected by the incident itself) among mass public shooters are estimated to be about 15 to 17 percent.

Studies that use a broader definition of mental illness and consider informal evidence indicative of mental health problems (e.g., statements by law enforcement or family before or after the incident) have found prevalence rates ranging from 30 to 60 percent. This informal evidence, which is often obtained subsequent to the incident, is invariably affected by the act of mass violence itself.

It does not suggest that mental illness is useful for predicting a subsequent mass shooting.

Of note, a study of 106 perpetrators of mass public shootings in the United States between 1990 and 2014 found that less than 5 percent of offenders had a history of involuntary commitment or adjudication of dangerousness that would have prohibited them from purchasing a firearm following the federal mental health background check.

Although most research supports that, overall, people with serious mental illness are over represented among mass public shooters, this does not imply that serious mental illness causes mass shootings, just as we cannot conclude that being a young man causes mass shootings.

Domestic Violence-Criminal Histories And Mass Shootings

Other researchers and analysts have noted that many mass shooters have a history of domestic violence. Using three mass shooting databases (whose underlying data sources include media reports, court records, and police records) and their own search of criminal records, Zeoli and Paruk (2020) analyzed 89 individuals who perpetrated a mass shooting (involving four or more fatalities, excluding the offender) between 2014 and 2017.

Of the 89 individuals, 28 (31 percent) had a history of suspected domestic violence. The authors identified that, of those 28, seventeen (61 percent) had prior interaction with the criminal justice system related to domestic violence, and six individuals had a felony or misdemeanor conviction for domestic violence.

Using a different definition of mass shooting (involving four or more casualties, including the perpetrator, and excluding felony-related mass shootings), Gu (2020) found that 36 percent of mass shooting incidents from 2014 to 2019 involved an offender with a history of domestic violence or violence against women.

“Public” Mass Shootings Are Responsible For Less Than 0.5 Percent Of All Homicides

Incidents of mass firearm violence galvanize public attention. There has been extensive media coverage of many incidents in the United States in which individuals have used firearms to kill large numbers of people. These mass public (emphasis added) shootings are rare events—they constitute less than 15 percent of all mass killings in the United States and are responsible for less than 0.5 percent of all homicides but they have far-reaching impacts on citizens’ mental health, anxiety, and perceptions of safety.

Editor’s note, see below for a discussion of “public” mass shootings.

No Firm Definitions of Mass Shootings

There is no standard definition of what constitutes a mass shooting, and different data sources—such as media outlets, academic researchers, and law enforcement agencies—frequently use different definitions when discussing and analyzing mass shootings. For instance, when various organizations measure and report on mass shootings, the criteria they use in counting such events might differ by the minimum threshold for the number of victims, whether the victim count includes those who were not fatally injured, where the shooting occurred, whether the shooting occurred in connection to another crime, and the relationship between the shooter and the victims.

These inconsistencies lead to different assessments of how frequently mass shootings occur and whether they are more common now than they were a decade or two ago.

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Because mass shootings that stem from domestic and gang violence are contextually distinct from high-fatality indiscriminate killings in public venues, some analysts have argued that they should be treated separately.

In their analyses of “mass public shootings,” Lott and Landes (2000) excluded any felony-related shooting, and Duwe, Kovandzic, and Moody (2002) excluded incidents where “both the victims and offender(s) were involved in unlawful activities, such as organized crime, gang activity, and drug deals.”

Similarly, other researchers have restricted analyses to events that occurred in a relatively public area and in which victims appeared to have been selected randomly.

However, others have claimed that this narrow definition ignores a substantial proportion of gun-related violence from family-or felony-related murder. Furthermore, determinants of whether victims were selected indiscriminately or whether the incidents were gang- or crime-related are, to some degree, subjective. Accurate information about the shooter’s motivations or connection to gangs may not have been included in police or news reports of the incidents.

How Many Mass Shootings Occur In A Year?

The number ranges from 10 to 503 in 2019 given group or research decisions as to what constitutes a mass shooting, the location (public or private), and the number of victims.

Have Mass Shootings Increased?

The data from multiple studies suggest a slight increase in the incidence rate of mass public shootings over the past four decades. From 2016 to 2018, the annual rate of mass public shooting incidents was about one incident per 50 million people in the United States.

Considering the number of fatalities in these shootings, this corresponds to approximately 0.4 percent of all homicides, or approximately 0.2 percent of all firearm deaths, over that period.

However, using an expanded definition of mass shootings that includes domestic-or felony-related killings, there is little evidence to suggest that mass shooting incidents or fatalities have increased.

Adjusted for changes in the size of the U.S. population, the incidence of all mass shootings (four or more fatally injured victims, excluding the offender, regardless of shooter motivation or circumstances) was highest in the late 1980s and early 1990s, averaging one incident per 10 million people from 1989 to 1993. More recently, between 2016 and 2018, the annual rate of all mass shooting incidents was about one incident per 14 million people.

Considering the number of fatalities in these mass shootings, this corresponds to approximately 0.8 percent of all homicides, or approximately 0.4 percent of all firearm deaths, over that period.

Thus, different choices about how to define a mass shooting result in different findings for both the prevalence of these events at a given time and their frequency has changed over time.

Locations And Motivations Change Over Time

Even the subset of mass public shootings seems to encompass a variety of offender types, and some researchers have suggested that the relative prevalence of these offender typologies has changed over time. When Capellan and colleagues considered incidents in which an offender used a firearm to kill or “attempt to kill” four or more victims in a public setting, they found that school shootings constituted the majority of mass public shooting incidents in the 1960s and 1970s, and workplace shootings became increasingly prevalent in the 1980s to 2000s.

The past decade has seen an increase in the percentage of mass public shootings that are posited to relate to fame-seeking on behalf of the individual or on behalf of a broader ideology.

Some researchers have suggested that this rise in fame and attention seeking motivations among mass public shooters has contributed to an escalation in the lethality of these incidents.

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Planning Mass Shootings-Public Statements

Although there are some noted differences across different types of mass public shootings, an overarching commonality is that most incidents are preceded by some level of planning by the shooter. Among active shooting cases from 2000 to 2013 for which sufficient information was available, 62 percent of offenders planned the attack for more than one month, and 9 percent planned for more than one year.

Focusing on incidents involving eight or more fatally injured victims, Lankford and Silver (2020) found that at least half of the 18 high-fatality mass public shootings between 2010 and 2019 involved a planning period of one year or longer.

About 40 percent of mass public shooters make some form of verbal or written threat (e.g., threats made in front of family or friends or posted to social media) prior to the incident.

Firearms Used

It is common for multiple firearms to be involved in public shootings: Various studies have indicated that multiple firearms were involved in an estimated 34 percent of active shooting incidents across 2000–2017, 42 percent of mass public shooting incidents across 1999–2013, and 79 percent of mass public shooting incidents that resulted in eight or more fatalities across 1966–2019.

In an analysis of mass public shootings in which shooters attempted to kill at least four individuals, Capellan and Jiao (2019) found that 80 percent of offenders had prior access to a firearm, although 41 percent of those individuals obtained additional firearms for the incident.

Handguns are the firearm most commonly involved in active shootings and mass shootings; semiautomatic rifles or “assault-style” weapons are used in an estimated 10 to 36 percent of active shootings and mass shootings.

The use of large-capacity magazines (LCMs) is more common in mass public shootings and high-fatality mass shooting incidents than it is in firearm crimes overall. The estimated prevalence of LCM involvement in mass shootings ranges from 20 to 60 percent, or from 45 to 60 percent when restricting the denominator to mass public shootings or high-fatality mass shootings.

For comparison, LCM-equipped firearms are estimated to constitute 22 to 36 percent of crime guns recovered by police in most urban jurisdictions.

Assault Weapons

When counting incidents involving an assault weapon or semiautomatic rifle per year, it ranges from 10 to 44.

Research On Policies That Might Reduce Mass Shootings

Because individuals who perpetrate mass shootings often die by suicide (or expect to be killed by someone trying to stop the shooting), standard deterrence strategies used in crime prevention are unlikely to work; increasing the certainty or severity of punishments seems unlikely to be effective when the perpetrator already expects to die in the mass shooting.

However, mass shootings are sufficiently rare that the statistical assumptions of these methods rarely hold, threatening the validity of the effect estimates and statistical inference and potentially resulting in spurious effects.

Even in studies that use models more appropriate for the distributional characteristics of mass shooting outcomes, the high degree of variability in mass shooting prevalence, injuries, and fatalities makes analyses of the effects of state policies on mass shooting outcomes subject to extremely low statistical power.

Using data from 1989 to 2014, researchers found a 15-percent increase in the number of state firearm bills introduced in the year following a mass shooting; states with Democratic-controlled legislatures did not show significant effects of firearm laws enacted, while states with Republican-controlled legislatures were significantly more likely to enact more-permissive gun laws subsequent to a mass public shooting incident in the state.

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If mass public shootings are a cause rather than (or in addition to) a consequence of firearm policy, models that fail to appropriately account for this reciprocal relationship may produce biased and misleading estimates of the effects of laws on mass shootings.

Finally, although extreme risk protection orders are most commonly requested because of concerns about self-harm, a detailed review of case records from 159 such orders issued in California found that 21 (13.2 percent) involved an individual who had access to or was planning to access firearms and expressed or exhibited behavior suggesting intent to perpetrate a mass shooting.

These analyses do not directly assess the causal effect of policies on mass shooting outcomes, but they can still provide important insights for crafting and implementing policies.

(Editor’s note, the following sentence is from another part of the document). Implementing broader violence prevention strategies rather than focusing specifically on the most extreme forms of such violence may be effective at reducing the occurrence and lethality of mass shootings.


National Institute Of Justice-Rand


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Op/Ed: Recognizing Mass Shooters And Potential Attacks In Public Places, Federal Research


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