Early Sunday morning at an Illinois bar, shots rang out and a Black security guard sprang into action to detain the suspect. However, when a responding police officer arrived on the scene, they unloaded their weapon and witnesses say they shot the wrong man.

Jemel Roberson, 26, was fatally shot dead by a Midlothian police officer responding at Manny’s Blue Room Bar about 4 a.m. Sunday. Roberson was working as a security guard at the bar when he was gunned down.

"Everybody was screaming out, 'Security!' He was a security guard," witness Adam Harris told WGN9. "And they still did their job, and saw a black man with a gun, and basically killed him."

The incident began when an inebriated group of men was asked to leave Manny's shortly before 4 a.m. Sunday. Although they left, said witnesses, someone eventually came back with a gun and opened fire.

The security guards returned fire and Roberson detained one of the men involved outside.

"He had somebody on the ground with his knee in back, with his gun in his back, like, 'Don’t move,'" Harris said told the local news station.

Although Roberson stopped the drunken gunman, an officer responding to the scene shot at the 26-year-old — killing him.

Four other people, including the suspected shooter, sustained non-life threatening injuries.

A spokeswoman for the Cook County Sheriff's Office said Roberson had a valid Firearm Owners ID (FOID) card, but did not have a concealed-carry license.

In a statement, Midlothian police confirmed two officers from the department responded to the scene of the shooting and that one of them opened fire.

"A Midlothian officer encountered a subject with a gun and was involved in an officer-involved shooting. The subject the officer shot was later pronounced deceased at an area hospital," Chief Daniel Delaney of the Midlothian Police Department said in a statement.

Friends said Roberson was a great musician who also had plans to become a police officer.

"Every artist he’s ever played for, every musician he’s ever sat beside, we’re all just broken because we have no answers," Rev. Patricia Hill from Purposed Church, where Roberson often played, said to WGN9. "He was getting ready to train and do all that stuff, so the very people he wanted to be family with, took his life."

"Once again, it’s the continued narrative that we see of shoot first, ask questions later," the Rev. LeAundre Hill added.

The Cook County Sheriff's Office is handling the criminal investigation of the original shooting, while the State Police Public Integrity Task Force is investigating the police-involved shooting.

A GoFundMe page has been set up to help cover funeral costs.