CHICAGO – A Chicago police officer has been charged with first-degree murder in connection with the shooting death of a 38-year-old man earlier this month on the city’s Northwest Side.

Officer Lowell Houser, 57, was arrested and charged Wednesday for the murder of Jose Nieves following the deadly encounter on the city’s Northwest Side. The criminal investigation was completed in 16-days, according to the Cook County state’s attorney.

The State’s Attorney’s Office said the charges came straight from Kim Foxx’s office. They said the FBI, Chicago Police Department, and IPRA had nothing to do with the decision, reported ABC7 News.

Police said Nieves was unarmed when he was shot and killed by the off-duty officer Jan. 2 in the 2500-block of North Lowell Avenue in the Hermosa neighborhood. The shooting occurred when an argument between the officer and victim escalated.

“The person who was shot did not have a weapon. That much we know. The officer’s weapon is the only one we found,” Chicago Police Department spokesman, Anthony Guglielmi said.

Nieves’ family filed a lawsuit last week alleging that the officer had clashed with the victim in the past and was emboldened by the culture at the Chicago Police Department, according to the report.

An attorney for the Nieves family said in a statement Wednesday: “The Nieves family is devastated by the loss of Jose. The State’s Attorney’s action today will not bring back Jose but is an important and swift step in the criminal justice process.”

Houser was stripped of his police powers the day after the shooting. The 28-year police veteran is being held without bond after apparently surrendering to the state’s attorney. He is set to appear at a bond hearing in Chicago Thursday.

Guglielmi released a statement Wednesday, saying, “The Chicago Police Department turned the case over to the States Attorney and the Independent Police Review Authority once the possibility of criminal violations were suspected. CPD will fully cooperate with the States Attorney throughout the judicial process.”

A memorial remains on the sidewalk outside Nieves’ apartment, where he died. Family said they had once been neighbors and had clashed before.

“My brother called 911 several times for help. He went through the right way of the system, going the right way, and he still was not heard,” said his sister Angelica Nieves.

At his funeral Jan, 9, the family indicated Officer Houser should be charged.

“If it had been any civilian out there, if it would have been me, if I would have shot somebody, I would have been locked up in jail,” Angelica said.