McDonald was killed in October 2014. The city's mayor has called for peace.
"I believe this is a moment that can build bridges of understanding rather than become a barrier of misunderstanding. I understand that the people will be upset and will want to protest when they see this video," Mayor Rahm Emanuel said. "We as a city must rise to this moment."
Chicago has been preparing for protests in advance of the video's release, which was ordered by a judge to happen no later than Wednesday.
McDonald was a black teenager. The officer who shot him, Jason Van Dyke, is white.
He was charged Tuesday with first-degree murder in McDonald's death and is being held without bond.
Chicago Police Superintendent Garry McCarthy acknowledged that residents "have a right to be angry."
Soon after the video's release, a group of protesters began marching, chanting "16 shots" and "We got to fight back!" McDonald died after being shot 16 times.
The NAACP said that McDonald's family and the community deserve action.
"People have a right to be angry, people have a right to protest, people have a right to free speech," McCarthy said. "But they do not have a right to commit criminal acts."
Van Dyke, who turned himself in to authorities Tuesday, is no longer being paid by the Police Department. Until Tuesday, he still worked for the department in a "limited duty position" as investigators probed the October 20, 2014, death.
"It is my determination that this defendant's actions -- of shooting Laquan McDonald when he did not pose an immediate threat of great bodily harm or death, and his subsequent actions of shooting Laquan McDonald while he lay on the ground after previously being struck by gunfire --- were not justified and they were not a proper use of deadly force by this police officer," Cook County State's Attorney Anita Alvarez said to announce charges against the officer.
Her announcement happened one day before the city's deadline to release video that shows the shooting. Until last week, officials had resisted such a release, fearing it could jeopardize investigations. Others said it could spur major protests in reaction to footage that even Van Dyke's attorney admits is "graphic, disturbing and difficult to watch."
Alvarez said the deadline moved up the timing of her announcement but did not dictate her decision to charge the officer with first-degree murder. She also defended the time it took her office to investigate by saying the case is complicated.
"Maintaining public safety is my No. 1 job, and I do not want the public to view this video without knowing this very important context that with these charges we are bringing a full measure of justice that this demands," she said.
Attorney: 'His actions were appropriate'
Authorities say McDonald was armed with a 3-inch knife when Van Dyke confronted him. The teen did not comply with "numerous police orders to drop the knife," the officer's attorney, Daniel Herbert, told the Chicago Tribune
Herbert has defended Van Dyke's actions, saying the officer "believed he was in fear for an attack and for the safety of anyone else on the scene."
"He's scared to death, but more than himself he's scared for his wife, his two kids," Herbert said of his client before charges were filed. "He knows in his heart of hearts that his actions were appropriate."
Van Dyke, 37, grew up in the Chicago area. He is married and has two children, ages 14 and 9.
The nearly seven-minute video released late Tuesday shows the dash-cam view as a patrol car approaches the scene. About five minutes and 20 seconds in, McDonald is seen running, then walking down a road toward several squad cars with flashing lights.
With his left hand near his pocket, McDonald veers away from two police officers, who have their guns drawn.
Seconds later, McDonald appears to spin around, then falls, writhing as shots keep hitting his body, sending puffs of smoke into the air.
At an afternoon hearing Tuesday, a judge temporarily denied bond for Van Dyke. Judge Donald Panarese Jr. plans to make a final determination on bond during another court hearing set for next Monday, so that he can have time to view the video.
"People viewing this videotape will have the brilliance and benefit of hindsight 20/20 vision," Herbert told reporters, saying the case needs to be tried in court, not in the media or on the streets.
"This is not a murder case, despite what you heard in the courtroom. It's truly not a murder case and we feel that we will be very successful in defending this case," the attorney said.
Pastor: 'Many ... feel betrayed'
According to Alvarez, Van Dyke was on the scene for less than 30 seconds before he started shooting. Citing a motorist who witnessed the shooting, she said that McDonald did not do anything threatening toward Van Dyke and the other responding officers before he was shot.
McDonald appeared to be moving away from the officers, while Van Dyke took at least one step toward McDonald with his weapon drawn, she said. While McDonald was falling to the ground, the officer took at least one more step toward him.
Activists have blasted Van Dyke. Mayor Emanuel joined them, releasing a statement on the charges.
"Across Chicago there are thousands of police officers who protect our communities every day with the highest professional standards. As the State's Attorney made clear, Jason Van Dyke's actions violated those standards and also the moral standards that bind our community together. Rather than uphold the law, he took the law into his own hands, and it's now up to the justice system to hold him accountable," the mayor said.
Emanuel met Monday with activists and community leaders to discuss the release and what it might mean for the city.
The Rev. Ira Acree said the mayor urged him and others to use their influence to ensure that any subsequent demonstrations are peaceful.
"Many in the community feel betrayed," Acree, a pastor at the Greater St. John Bible Church, told reporters after the meeting. "Protests are imminent."
Chicago Tribune columnist John Kass has said the video
"could tear Chicago apart."
"Chicago is on the tipping point," the Rev. Roosevelt Watkins said, according to CNN affiliate WLS-TV.
"We could be just like Ferguson."
Watkins was referring to Ferguson, Missouri,
which imploded in protests and riots after a white police officer shot to death unarmed black teen Michael Brown
in 2014. Unrest in the St. Louis suburb lasted for months afterward.
One Twitter user compared McDonald's death to that of Walter Scott, a black man in South Carolina who was killed by an officer after being pulled over, reportedly for a broken brake light, and later struck in the back as he was running away from police.
City reaches settlement with family
But what happened in Chicago differs from Ferguson in a few ways.
McDonald was armed, unlike Brown. According to toxicology test results, McDonald had PCP in his system.
And Van Dyke confronted him knowing that McDonald had "punctured a tire on a police car," according to his attorney.
Another major difference is that McDonald's final moments were captured on video.
The city agreed in April to pay $5 million to McDonald's family, though the family had not filed a lawsuit.
McDonald was a ward of the state at the time of his death, according to a spokeswoman with the Illinois Department of Children and Family Services. A few days before he was killed, DCFS gave him over to the custody of a relative, she said.
She also said that McDonald was the alleged victim in two abuse investigations. One happened in 2000; the other in 2003.
McDonald attended Sullivan House, an alternative school, for about two months, according to the principal there.
Thomas Gattuso remembered McDonald as someone who was outgoing, jovial, talkative and funny. He'd thought about playing basketball and wanted to get his life on track, the principal said.
"We have a tragic ending to -- unfortunately -- a tragic life of a young man, who was betrayed on a number of different levels," said McCarthy, the police superintendent.