CHICAGO — The family of an unarmed man shot dead by a Chicago police officer six years ago announced Thursday they will seek the appointment of a special prosecutor to investigate the shooting.

Officers responding to a domestic abuse call in June 2011 shot Flint Farmer multiple times. A squad car video shows Officer Gildardo Sierra shooting the 29-year-old Farmer three more times as he lay on the ground. The Cook County medical examiner’s office concluded the three shots in Farmer’s back were the fatal wounds.

Emmett Farmer, the slain man’s father, said he’s seeking a special prosecutor in an attempt “to get justice for my son.” His lawyers say they will appear before Cook County Circuit Judge Leroy Martin next week on their petition.

“I just believe that now is the time for someone to do something,” Farmer said of their efforts.

State’s Attorney Kim Foxx has said in the past that she believes the state’s attorney’s office has an inherent conflict of interest in prosecuting police-involved shootings because of its close working relationship with the police.

State’s attorney spokesman Robert Foley said the office is “reviewing the petition” that was filed Thursday. Sierra couldn’t be reached for comment.

In 2013, then- State’s Attorney Anita Alvarez declined to charge Sierra. A police report claimed Farmer pointed a cellphone at officers.

The Chicago Tribune reports a court filing by the Farmer family contends Sierra admitted he drank “multiple” beers before he went to work the night of Farmer’s shooting. However, the city waited more than five hours to give him a breath test.

Last year, Chicago’s Independent Police Review Authority determined Sierra was unjustified in shooting Farmer. The decision came nearly a year after Sierra resigned from the police department.

The Chicago City Council in 2013 approved an award of $4.1 million to Farmer’s family.