MARION COUNTY, Ind. – The man accused of murdering Southport police Lt. Aaron Allan has been charged with his murder.

A driver, upside down and suspended in his overturned vehicle, reportedly “became hysterical” and fatally shot Allan who came to his rescue last week, according to court papers.

Jason Brown, 28, struck Allan 11 times as the officer was partially inside of his vehicle’s rear passenger side, trying to render aid, prosecutors say.

Allan, 38, later died of multiple gunshot wounds at a hospital after the shooting on Thursday, a probable cause affidavit said.

The Marion County Prosecutor’s Office charged Brown with murder on Tuesday. Brown was also charged with possession of marijuana, a misdemeanor, reported CNN.

It is not known if Brown was impaired at the time, or whether or not he sustained injuries from the rollover accident.

His initial hearing is scheduled for Thursday. It wasn’t immediately clear if Brown had an attorney.

Related: Sometimes a Picture Really is Worth a Thousand Words: What Law Enforcement Officers Can Learn from Lt. Aaron Allan

Brown’s passenger, known as H.L. in the affidavit, told police Brown picked him up and began speeding and weaving his 2004 BMW around vehicles after they left a gas station, according to the affidavit.

Brown struck a curb, drove across the median and hit another curb, flipping the vehicle, which landed upside down on an Indianapolis street.

The passenger managed to get out of the vehicle and wait for help, according to the CNN report.

Around 2:30 p.m., Allan was dispatched to the collision, the Indianapolis Metropolitan Police Department said. A Homecroft police officer also responded.

Allan stuck his head inside the passenger side and spoke with the Brown who had been driving. He “became hysterical,” said the other responding officer.

The second officer said Allan tried to calm Brown and reassure him that help was on the way, reported CNN.

One witness, a nurse, who stopped to help after seeing the BMW go airborne, told police the driver “became very agitated and belligerent and began cursing,” the affidavit said.

A second witness, also a nurse, said from the driver’s side door he saw the suspect “trying to reach for something behind his back and observed a pistol come out,” the affidavit said.

According to the affidavit, Brown fired as his passenger was talking to police.

Major C.T. Bowman with the Homecroft Police Department told investigators that he heard 10-12 gunshots. There was a pause, he said, and he then heard two to three more.

Consequently, Allan managed to stumble back a few feet from the BMW before collapsing, the affidavit said. His gun remained holstered.

Two officers at the scene fired at the BMW, hitting Brown, including an off-duty reserve sheriff’s deputy who stopped to help, the affidavit said.

One officer cut Brown’s seat belt and police pulled him from the vehicle. The officer saw a semi-automatic pistol on the BMW’s roof, the affidavit said.

Brown, who was shot in his right cheek, collarbone and left arm and was taken to a local hospital, the affidavit said.

Authorities said that one round from Brown struck Allan in the heart.

“Lieutenant Allan was a hard worker and today was no different,” Southport Police Chief Thomas Vaughn said Thursday. “He responded to a crash with urgency to preserve life. Tragically, his was lost.”

Allan had more than 20 years of experience in law enforcement. He joined the Southport department nearly six years ago, Indianapolis Metropolitan Police said.

In a statement, the Southport department said many witnesses expressed support and sympathy for the loss of Allan. “Thank you for making a difficult day a little easier,” a Southport detective said.

Lt. Allan’s wife, Stacy, said her husband “was my rock.”

“He was not only proud to wear the badge, he was a proud father and husband,” she said in a statement. “There is no room in my heart for anger or hate, only peace knowing Aaron died doing what he loved.”

(Photo: Southport Police)