CHICAGO (AP) — The latest on the shooting of a black teenager by a white Chicago police officer. (All times local):

9:15 a.m.

A white Chicago police officer who shot a black teenager 16 times has turned himself in at the Cook County courthouse where he’s expected to face a murder charge.

Trailed by reporters and photographers, Officer Jason Van Dyke walked into the courthouse Tuesday morning.

An official close to the investigation told The Associated Press’ Don Babwin that county prosecutors are expected to charge him with murder on Tuesday.

The official spoke on condition of anonymity so as not to pre-empt the expected charges.

The Oct. 20, 2014, shooting of 17-year-old Laquan McDonald was captured on a squad car’s dashcam, and a judge has given the city until the end of Wednesday to release it publicly.

Several people who have seen the video say it shows McDonald armed with a small knife and walking away from several officers. An autopsy report says he was shot at least twice in his back.

As reported earlier:

A white Chicago police officer who shot a black teenager 16 times was expected to be charged with murder Tuesday, just a day ahead of a deadline for the city to release a squad-car video of the shooting.

Veteran officer Jason Van Dyke is expected to be indicted in the killing of 17-year-old Laquan McDonald, an official close to the investigation told The Associated Press. The official spoke on condition of anonymity so as not to pre-empt an announcement of the charge.

City officials and community leaders have been bracing for the release of the video, fearing an outbreak of unrest and demonstrations similar to those that occurred in Baltimore, Ferguson, Missouri and other cities after young black men were slain by police or died in police custody. The judge ordered the dash-cam recording to be released by Wednesday after city officials had argued for months it couldn’t be made public until the conclusion of several investigations.

Several people who have seen the video say it shows the teenager armed with a small knife and walking away from several officers on Oct. 20, 2014. They say Van Dyke opened fire from about 15 feet and kept shooting after the teen fell to the ground. An autopsy report says McDonald was shot at least twice in his back. It also said PCP, a hallucinogenic drug, was found in the teen’s system.

An attorney for Van Dyke did not respond to messages from the AP seeking comment.

Chicago police also moved late Monday to discipline a second officer who had shot and killed an unarmed black woman in 2012 in another incident causing tensions between the department and minority communities. Superintendent Garry McCarthy recommended firing Officer Dante Servin for the shooting of 22-year-old Rekia Boyd, saying Servin showed “incredibly poor judgment.” A jury had acquitted Servin of involuntary manslaughter and other charges last April.

Mayor Rahm Emanuel called together a number of community leaders Monday to appeal for help calming the emotions that have built up over the McDonald shooting. Some attendees said city officials waited too long to ask for their involvement.

“You had this tape for a year and you are only talking to us now because you need our help keeping things calm,” one of the ministers, Corey Brooks, said after the meeting.

Ira Acree, who described the meeting with Emanuel as “very tense, very contentious,” said the mayor expressed concerns about the prospect of any demonstrations getting out of control.

Another minister who attended, Jedidiah Brown, said emotions were running so high that there would be no stopping major protests once the video is released.

The fears of unrest stem from longstanding tensions between the Chicago police and minority communities, partly due to the department’s dogged reputation for brutality, particularly involving blacks. Dozens of men, mostly African American, said they were subjected to torture at the hands of a Chicago police squad headed by former commander Jon Burge during the 1970s, ’80s and early ’90s, and many spent years in prison. Burge was eventually convicted of lying about the torture and served 4½ years in prison.

The two ministers said blacks in the city are upset because the officer, though stripped of his police powers, has been assigned to desk duty and not fired.

“They had the opportunity to be a good example and a model across the country on how to improve police and community relations and they missed it,” Acree said.

The Police Department said placing an officer on desk duty after a shooting is standard procedure and that it is prohibited from doing anything more during the investigations.