Updated

The police officer who fatally shot a black armed security guard as he held down a gunman outside a bar in Chicago’s suburbs on Sunday, had told the guard to drop his gun and get on the ground before ultimately firing his weapon, according to witnesses cited by Illinois State Police.

COP ACCIDENTALLY KILLS SECURITY GUARD AT BAR IN CHICAGO SUBURBS: REPORT

The security guard, Jemel Roberson, 26, had apprehended a gunman who had reportedly opened fire and injured four at Manny’s Blue Room Lounge in Robbins around 4 a.m.

Officers from the Robbins and Midlothian Police Departments, along with other suburban police officers responded to a call of shots fired, ISP said in a news release.

According to the release, a Midlothian officer encountered Roberson “with no markings readily identifying him as a Security Guard, armed with a gun in the west parking lot.”

An attorney representing Roberson’s family said Roberson was wearing a hat with “security” across the front. Attorney Gregory Kulis filed a civil rights lawsuit seeking more than $1 million on behalf of Roberson's mother, Beatrice Roberson.

FAMILY OF CHICAGO SECURITY GUARD SHOT DEAD BY COP FILES LAWSUIT

One of the two Midlothian officers gave “multiple verbal commands to drop the gun and get on the ground” before shooting Roberson, witnesses said.

Officers provided medical assistance to the four victims and Roberson, the release said. Roberson was taken to a hospital where he was pronounced dead.

The Cook County Medical Examiner’s office ruled Roberson’s death a homicide and said he was shot multiple times. The Cook County Sheriff’s Police Department is continuing its investigation. The officer's identity has not been released.

Authorities are asking anyone who witnessed the shooting to call ISP at (847) 294-4400 or Cook County Sheriff’s Police Department at (847) 635-1188. Callers will anonymous.

The Associated Press contributed to this report.