CHICAGO—Embattled mayor Rahm Emanuel offered a plaintive apology on Wednesday for his responsibility in the city’s handling of the shooting death of a black teenager by a Chicago Police officer.

Emanuel said the city is at a “defining moment” and that Chicago needs to go through a “painful but honest reckoning” not just in the case of last year’s shooting death of Laquan McDonald but “over decades” of mounting public distrust of the city’s police department.

“The first step in that journey is my step, and I’m sorry,” Emanuel said in an emotional address to Chicago’s city council. “What happened on Oct. 20, 2014 should have never happened. Supervision and leadership in the police department and oversight agencies that were in place failed. And that has to change.”

The mayor, a former three-term U.S. congressman and chief of staff to President Obama, has been under fire, since the city was forced by court order more than two weeks ago to release police dashboard video of the shooting death of McDonald, who was shot 16 times by officer Jason Van Dyke.

Protesters who have taken to the streets of Chicago have called for both the mayor and Cook County State’s Attorney Anita Alvarez to step down in the wake of the video’s release. The Justice Department also announced on Monday that it was launching a patterns and practices investigation of the police department.

Police and police union officials said after the shooting that McDonald, who was holding a knife and had PCP in his system when he was killed, lunged at Van Dyke. But the police video showed that McDonald was veering away from Van Dyke when the officer fired. Van Dyke continued to fire for about 13 seconds after McDonald was on the ground, the video shows.

At least five police officers who were at the scene backed up much of Van Dyke’s account in statements to investigators after the shooting.

Prosecutors announced they were charging Van Dyke on the same day that the video was released by the city, more than 13 months after McDonald was gunned down on a city street.

Emanuel had long resisted releasing the dashcam video, citing ongoing federal and state criminal probes, but was forced to after an independent journalist successfully sued the city for the video under state’s Freedom of Information law.

Following the video’s release, Emanuel fired Chicago Police superintendent Garry McCarthy after initially resisting calls to do just that. He also ousted the head of the Independent Police Review Authority, which is tasked with investigating serious allegations of police misconduct. Since 2007, the agency has found only two police shootings unjustified among more than 400 cases it has investigated.

“These facts defy credibility,” Emanuel said.

Emanuel’s standing in the city has taken a beating since the release of the video.

A  poll published on Tuesday shows that more than half of Chicagoans believe Mayor Rahm Emanuel should resign as a result of his handling of the McDonald video.

More than 51% of likely voters said Emanuel should resign, while 29% said he should not step down, according to the poll commissioned by The Insider, a newsletter published by Illinois Observer.

“I know that I personally have a lot of work to do to win back the public’s trust and that words are not enough,” Emanuel said.

In the nearly 40-minute speech, Emanuel vowed the city would “not to shrink from the challenge” of making reforms needed to bolster public trust in a department that has been beset for years by allegations of torturing and beating suspects.

“Laquan McDonald’s death was totally avoidable,” Emanuel said. “Our only choice is to do everything in our power to right that wrong.”

Chicago is latest American city that has been forced to deal with long-simmering distrust of police departments in the African-American community following the release of video that shows police using deadly force. Cleveland, New York and North Charleston, S.C. are among cities that have faced outrage from the public following the release of disturbing videos showing fatal use of force by police officers.

“When African American mothers, fathers and grandparents feel it is necessary to train their sons and daughters to behave with extreme caution when they are are pulled over by police and have both hands visible on the wheel, what does that say?” Emanuel said.