Don Babwin ?and Jason Keyser

CHICAGO: A white Chicago police officer who shot a black teenager 16 times last year was charged with first-degree murder Tuesday, hours before the city released a video of the killing that many people fear could spark unrest.

City officials and community leaders have been bracing for the release of the dash-cam video, fearing the kind of turmoil that occurred in cities such as Baltimore and Ferguson, Mo., after young black men were slain by police or died in police custody.

A judge ordered that the recording be made public by Wednesday. Moments before it was released, the mayor and the police chief appealed for calm.

“People have a right to be angry. People have a right to protest. People have a right to free speech. But they do not have a right to ... criminal acts,” police Superintendent Garry McCarthy said.

The relevant portion of the video runs for less than 40 seconds and has no audio.

Laquan McDonald, 17, swings into view on a four-lane street where police vehicles are stopped in the middle of the roadway. As he jogs down an empty lane, he appears to pull up his pants and then slows to a brisk walk, veering away from two officers who are emerging from a vehicle and drawing their guns.

Almost immediately, one of the officers appears to fire from close range. McDonald spins around and crumples to the pavement. The second officer simultaneously lowers his weapon.

The car with the camera continues to roll forward until the officers are out of the frame. Then McDonald can be seen lying on the ground, moving occasionally. At least two small puffs of smoke are seen coming off his body as the officer continues firing.

In the final moments, an officer kicks something out of McDonald’s hands.

Police have said the teen had a knife. Cook County State’s Attorney Anita Alvarez said Tuesday that a 3-inch knife with its blade folded into the handle was recovered from the scene.

Shortly after the video’s release, protesters began marching through streets. Several hundred people blocked traffic on the near West Side. Some circled police cars in an intersection and chanted “16 shots.”

“I’m so hurt and so angry,” said Jedidiah Brown, a South Side activist and pastor who had just seen the video. “I can feel pain through my body.”

Protesters were accompanied by many police officers, and no violence was immediately reported.

City officials spent months arguing that the footage could not be made public until the conclusion of several investigations. After the judge’s order, the investigations were quickly wrapped up and a charge announced.

Alvarez defended the 13 months it took to charge officer Jason Van Dyke. She said cases involving police present “highly complex” legal issues and that she would rather take the time to get it right than “rush to judgment.”

Alvarez said concern about the impending release prompted her to move up the announcement of the murder charge.

“It is graphic. It is violent. It is chilling,” she said. “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 Van Dyke 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 from Oct. 20, 2014.

“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.

Months after McDonald’s death, the city agreed to a $5 million settlement with his family, even before relatives filed a lawsuit.