CHICAGO — The family of an unarmed man shot dead by a Chicago police officer six years ago is demanding 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 him three more times while the 29-year-old Farmer lay on the ground. The Cook County medical examiner’s office concluded those were the fatal wounds.

Emmett Farmer said Thursday he is seeking justice for his son. His lawyers say they will appear before a judge next week on their petition.

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.