A police officer responding to a shooting at a bar in Cook County, Illinois, reportedly killed a black security guard who witnesses say had pinned the suspect on the ground.

The incident began on Sunday morning when security at Manny’s Blue Room Bar in Robbins, a south suburb of Chicago, asked a group of drunken men to leave, witnesses told WGN. One of the men returned to the bar and opened fire. Security returned fire and one of the guards, 26-year-old Jemel Roberson, managed to apprehend the suspect.

Police officers soon arrived at the bar in response to reports of a shooting and saw Roberson with a gun in his hand. Witnesses said that they tried to tell the officers that Roberson was a security guard. One of the officers then shot Roberson, who later died at Christ Medical Center. Four other people, including the suspected shooter, suffered nonfatal injuries.

Authorities have released few details about the shooting, only mentioning that the violence arose out of an argument. A spokesperson also noted that Roberson had a valid firearm license, though he did not have one for concealed carry. The officer who shot Roberson is a member of the police department in nearby Midlothian. The Illinois State Police will be reviewing the officer’s actions, while the Cook County Sheriff’s Office will be investigating the bar-room shooting.

“How in the world does the security guard get shot by police?” asked Walter Turner, a pastor at New Spiritual Light Baptist Church, where Roberson was an organist. “A young man that was literally doing his job and now he’s gone.”