The family of a black security guard who was killed by police while he was working at a nightclub in south suburban Robbins has filed a federal lawsuit.

Jemel Roberson was armed and working security at Manny’s Blue Room around 4 A.M. on Sunday when a shooting occurred, according to the Cook County Sheriff’s office. Witnesses say a white police officer from nearby Midlothian arrived on the scene and fatally shot Roberson while he was subduing someone, according to Greg Kulis, an attorney for Roberson’s family.

When police arrived at the scene, Roberson was holding “somebody on the ground with his knee in his back, with his gun in his back,” witness Adam Harris told WGN-TV.

“Everybody is screaming out, ‘He’s a security guard,’” Harris said.

Roberson, a father of a 9-month-old boy, was licensed to carry a firearm, Ansari said.

Kulis said “there was security trying to do their job and law enforcement kills him.”

Four other people were shot during the incident and left with non-life-threatening injuries, according to the sheriff’s office.

Roberson’s family has filed a lawsuit against the Village of Midlothian and the officer, whose name has not been released. 

Attorney Gregory Kulis filed a civil rights lawsuit seeking more than $1 million on behalf of Roberson’s mother, Beatrice Roberson. He said Jemel Roberson was dressed in black but wearing a hat with the word “security” when he was shot.

Kulis also echoed witness reports that Roberson was holding down another man outside the bar when the officer arrived and shot him.

The lawsuit alleges the shooting was ”unprovoked” and “unjustified.”

The Midlothian Police Department did not return requests for comment Monday.

No details have been released about the officer. Roberson, who was black, was the only person killed. The other four people who were shot suffered wounds that weren’t considered life-threatening, Ansari said.

At an impromptu vigil held outside of Manny’s on Monday night, Irwin Smith, who said he worked at the club with Roberson, described what he saw.

“Man lost his life senseless, saving others lives,” Smith said on Facebook Live. “For a a guy who risked his life for over 100 people, to lose his life—there is not a justifiable reason.”

A man who said he was Roberson’s god-brother and a fellow security guard said that, along with being angry and hurt, he was also proud.

“He protected everybody and put his life at stake,” said the man, who did not give his name. “Because at the end of the day, that’s what the job requires us to do.”

The Rev. Marvin Hunter said Roberson was “an upstanding young man” and a promising keyboard player at his and several other area churches.

It is with great sadness that we inform you of the tragic passing of 2010 Lane Tech graduate and Lane Tech Basketball alumn, Jemel Roberson. We pass along our deepest condolences to the friends and family of Jemel. Jemel had a big smile and a bigger heart. You will be missed. pic.twitter.com/gpdrI6qQtc

— Lane Tech Basketball (@LaneTechHoops) November 12, 2018

Roberson was trying to “get enough money together for a deposit on a new apartment,” said Hunter, the great-uncle of Laquan McDonald, a black teenager fatally shot by a white Chicago police officer in a high-profile 2014 case.

Roberson also had hopes of someday becoming a police officer, according to his son’s mother.

“This was going to be my baby’s first Christmas with his dad and now he’s going to miss out on everything,” said Avontea Boose.

A GoFundMe page has also been set up to raise money for funeral costs. Family and friends held a vigil Monday night.

The shooting is being investigated by the Cook County Sheriff’s office and Illinois State Police.

The Village of Robbins has ordered Manny’s to temporarily close pending an investigation.

The Associated Press contributed reporting to this story.