CHICAGO (AFP) - Racial tensions soared here on Tuesday (Nov 24) as officials released a graphic video of a police officer shooting a black teen, shortly after he was charged for the death.
Crowds of demonstrators gathered for an organised protest in Chicago, but there were only small scuffles with law enforcement.
The dashcam video shows officer Jason Van Dyke open fire 16 times on Laquan McDonald, 17.
Shot from an approaching cruiser, it shows McDonald run down the middle of the street towards a cruiser, hitch up his pants and then start to walk away from Van Dyke and his partner.
His body then spins and strikes the pavement. McDonald lifts his head, moves an arm and then a cloud from another gunshot rises up from his chest as he lays in a fetal position.
He does not move as an officer enters the frame for just long enough to kick a knife away from his prone hand.
None of the officers approach McDonald to try to help him as he bleeds out on the street, writhing once in the remaining minute of video.
Prosecutors said Van Dyke opened fire just 30 seconds after his cruiser pulled up to the scene and six seconds after stepping out of it.
"It is graphic, it is violent, it is chilling," Cook County State's Attorney Anita Alvarez told reporters after charging Van Dyke with first-degree murder.
"To watch a 17-year-old young man die in such a violent manner is deeply disturbing and I have absolutely no doubt this video will tear at the hearts of all Chicagoans."
McDonald - who police said was holding a knife when he was shot and had earlier slashed the tires of a police cruiser - made no threatening gestures to justify the use of deadly force, Ms Alvarez said.
It was the first time a Chicago police officer has been charged with first-degree murder for an on-duty fatality in more than 30 years, the Chicago Tribune reported.
Mayor Rahm Emanuel appealed for calm.
"I understand people will be upset and will want to protest when they see this video," he told reporters.
"It is fine to be passionate, but it is essential that it remains peaceful."
Police Superintendent Garry McCarthy said his officers would ensure people were allowed to protest peacefully but warned they would be "intolerant of criminal behaviour".
"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 commit criminal acts," he told reporters.
McDonald's family has joined community leaders and city officials in appealing for peace.
"No one understands the anger more than us but if you choose to speak out, we urge you to be peaceful," they said in a statement released to local media.
"Don't resort to violence in Laquan's name. Let his legacy be better than that."
The city approved a US$5 million settlement for McDonald's family in April and the federal authorities are investigating the case.
Police had initially said McDonald was high on PCP, acting erratically and lunged at the officers with a knife.
The graphic video is the latest in a string of police shootings caught on camera that have sparked mass - and sometimes violent - protests and engulfed the United States in a debate over racism and the use of deadly force by police.
It comes a day after three men opened fire on protesters in Minneapolis, Minnesota who were demonstrating in response to another fatal police shooting.
Five people were wounded, none seriously, and police arrested two suspects.
The Black Lives Matter demonstration was held over the police killing of another black man, 24-year-old Jamar Clark.
"White supremacists attacked the #4thPrecinctShutDown in an act of domestic terrorism," the group wrote on its Facebook page. "We won't be intimidated."
Minneapolis police said Clark died in a struggle with police responding to a domestic disturbance on Nov 15.
His brother Eddie Sutton thanked demonstrators for their vigilance but asked them to suspend their protests, according to the Minneapolis Star Tribune.
"In light of tonight's shootings, the family feels out of imminent concern for the safety of the occupiers, we must get the occupation of the Fourth Precinct ended and onto the next step," Mr Sutton said.
Mayor Betsy Hodges praised police for swiftly two suspects in the "abhorrent shooting" and said the city is "sparing no efforts to bring any and all those responsible to justice".
Initial police reports indicated that three white men fired into the crowd of demonstrators at 10.45 pm on Monday.