Illinois' top prosecutor on Tuesday asked the U.S. Department of Justice to investigate whether Chicago police practices violate federal law.
The request by Illinois Attorney General Lisa Madigan comes on the same day that Chicago's police chief was fired following the release of dash-cam video that showed an officer fatally shoot 17-year-old Laquan McDonald last year.
"The shocking death of Laquan McDonald is the latest tragedy in our city that highlights serious questions about the use of unlawful and excessive force by Chicago police officers and the lack of accountability for such abuse," Madigan said in a statement. "Trust in the Chicago Police Department is broken."
The letter to U.S. Attorney General Loretta E. Lynch asks the Justice Department's Civil Rights Division to review police use of deadly force and police investigations into the use of deadly force, as well as police training and whether a pattern of discrimination exists.
Chicago Mayor Rahm Emanuel said he asked police Superintendent Garry McCarthy to step down, saying "the public trust in the leadership of the department has been shaken and eroded."
"As Mr. McCarthy knows, a police officer is only as effective as when he has the trust of those he serves," Emanuel said.
Sixteen shots were fired at McDonald on Oct. 20, 2014. The officer who fired those shots, Jason Van Dyke, 37, was charged last week with first-degree murder.
McDonald was armed with a knife and had taken the drug PCP, prosecutors have said. Van Dyke's attorneys have said the shooting was justified because the officer felt threatened.