CHICAGO (TIP): Chicago Mayor Rahm Emanuel said Tuesday, December 1, he has asked for the resignation of Chicago Police Superintendent Garry McCarthy.

The announcement at a news conference came amid angry protests in Chicago over the way the city responded when a white police officer shot a black teenager 16 times in October 2014. Dashboard camera footage of Laquan McDonald’s killing was released last week after a judge ordered it be made public.

“Superintendent McCarthy knows that a police officer is only as effective as when he has the trust of those he serves,” said Emanuel, speaking at City Hall.

McCarthy was not at the news conference. But the mayor’s office told CNN the superintendent had, in fact, resigned.

The mayor went on to describe a new task force on law enforcement accountability that will review how the city trains and oversees its police officers. It will include five Chicagoans who have been leaders in the justice system. Chicago native and former Massachusetts Gov. Deval Patrick will be a senior adviser to the group, Emanuel said.

Later Tuesday, Illinois Attorney General Lisa Madigan said she sent a letter to the U.S. attorney general asking the Department of Justice’s Civil Rights Division to open an investigation into the Chicago Police Department to see whether its practices violate the Constitution and federal law.

“Trust in the Chicago Police Department is broken,” Madigan said in a statement. “Chicago cannot move ahead and rebuild trust between the police and the community without an outside, independent investigation into its police department to improve policing practices.”

The turmoil in Chicago isn’t unique to the city. For more than a year Black Lives Matter activists and others have tried to call attention to an assertion that some police across the country discriminate against black people. They point to cases in New York; Ferguson, Missouri; Baltimore and other cities, where they say police have used excessive and deadly force against black males.

In Chicago, the outrage has been focused on the killing of McDonald. Dashboard camera footage from October 2014 shows the 17-year-old walking in the middle of a street toward squad cars while holding a knife. He then veers away and turns his back to police, and immediately is shot multiple times.

Jason Van Dyke, the officer who shot McDonald, has been charged with first-degree murder.