CHICAGO (AP) — A white Chicago police officer who shot a black teenager 16 times was charged with first-degree murder Tuesday, a day before the deadline a judge set for the city to release a squad-car video of the killing that officials fear will spark unrest.

A judge denied Officer Jason Van Dyke bond at a noon hearing. About an hour later, Cook County State's Attorney Anita Alvarez held a news conference where she defended the amount of time it took to charge the officer in the Oct. 20, 2014, killing of 17-year-old Laquan McDonald.

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 cities including Baltimore and Ferguson, Missouri, after young black men were slain by police or died in police custody. The judge who ordered the dash-cam recording to be released said it must be put out by Wednesday after city officials had argued for months it couldn't be made public until the conclusion of several investigations.

Alvarez said Tuesday that cases involving police officers present "highly complex" legal issues and she would rather take the time to get it right than "rush to judgment." She said the impending release of the video prompted her to move up the announcement of the charge out of concern the footage would spark violence.

"It is graphic. It is violent. It is chilling," she said of the video. "To watch a 17-year-old young man die in such a violent manner is deeply disturbing. I have absolutely no doubt that this video will tear at the hearts of all Chicagoans."

But she insisted that she made a decision "weeks ago" to charge the officer and the video's ordered release did not influence that.

Some community leaders said there was no doubt that Alvarez only brought charges because of the order to release the video.

"This is a panicky reaction to an institutional crisis within the criminal justice system," said the Rev. Jesse Jackson, who said he hoped to see "massive" but peaceful demonstrations.

The city's hurried attempts to defuse tensions also included a community meeting, official statements of outrage at the officer's conduct and an abrupt announcement Monday night that another officer who's been the subject of protests for months might now be fired.

Activists and journalists have long pressed for the video's release only to be told that it had to be kept private as long as the shooting was under investigation. After the judge's order to release it, the investigation was quickly wrapped up and a charge announced.

"You had this tape for a year and you are only talking to us now because you need our help keeping things calm," the Rev. Corey Brooks said of Monday night's community gathering with Mayor Rahm Emanuel.

Several people who have seen the video say it shows the teenager armed with a small knife and walking away from several officers. 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.

Police were responding to complaints about someone breaking into cars and stealing radios.

Van Dyke was the only officer of the several who were on the scene to open fire. Alvarez said the officer emptied his 9 mm pistol of all 16 rounds and that he was on the scene for just 30 seconds before he started shooting. She said he opened fire just six seconds after getting out of his vehicle and kept firing even though McDonald dropped to the ground after the initial shots.

Assistant State's Attorney Bill Delaney said at the hearing Tuesday the shooting lasted 14 to 15 seconds and that McDonald was on the ground for 13 of those seconds.

Police say the teen had a knife, and Delaney said a 3-inch knife was recovered from the scene.

Van Dyke's attorney, Dan Herbert, maintains his client feared for his life and acted lawfully and that the video about to be released doesn't tell the whole story. Van Dyke, though stripped of his police powers, has been assigned to desk duty since the shooting.

Herbert said the case needs to be tried in a courtroom and "can't be tried in the streets, can't be tried on social media and can't be tried on Facebook."

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 judge acquitted Servin of involuntary manslaughter and other charges last April, and Alvarez was accused of having not prosecuted the case properly.

Jackson said a special prosecutor should oversee the Van Dyke case instead of Alvarez's office.

None of the city's outreach will be able to stop protests once the video is released, said Jedidiah Brown, another of the pastors who attended the meeting with Emanuel. Emotions are running too high, he added.

The fears of unrest stem from long-standing tensions between Chicago police and its 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 from 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.

___

This story has been corrected to show that a judge, not a jury, acquitted Servin of involuntary manslaughter.

___

Associated Press writers Sophia Tareen and Michael Tarm contributed to this report.