Chicago Police Superintendent Garry McCarthy (L) and Mayor Rahm Emanuel arrive for a press conference to address the arrest of Chicago Police officer Jason Van Dyke on November 24, 2015
Chicago (AFP) - Racial tensions soared in Chicago as officials released a graphic video of a police officer shooting a black teen 16 times, shortly after he was charged for the death.
The "chilling" 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.
Dozens of demonstrators marched through the city's busy streets, but there were only small scuffles with law enforcement and three arrests reported by the early hours of Wednesday morning.
The dashcam video shows officer Jason Van Dyke open fire on Laquan McDonald, 17.
"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."
Shot from an approaching police vehicle, 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.
McDonald -- who 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, 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.
- 'Build bridges' -
City officials, who had tried to block the video from going public, were ordered by a judge to release it no later than Wednesday.
Alvarez said she had planned to wait until a federal investigation was complete but decided to press charges against Van Dyke prior to the video's release "in the interest of public safety."
Mayor Rahm Emanuel appealed for calm and said he hoped the city could use the incident as an opportunity to "build bridges of understanding" between police and young men like McDonald.
"We as a city must rise to this moment," he told reporters.
Police Superintendent Garry McCarthy said that while "people have a right to be angry" and to protest peacefully, his officers would be "intolerant of criminal behavior."
McDonald's family joined community leaders and city officials in appealing for calm.
"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 $5 million settlement for McDonald's family in April.
Police had initially said McDonald was high on PCP, acting erratically and lunged at the officers with a knife.
- Minneapolis protest attacked -
The video was released a day after three men opened fire on protesters in Minneapolis, Minnesota who were demonstrating in response to the fatal police shooting of Jamal Clark, 24.
Five people were wounded, but none seriously.
Police arrested two individuals, a 23-year-old white man and 32-year-old Hispanic man, releasing the latter after questioning.
They also took into custody two additional white men, a 26-year-old and 21-year-old, after they turned themselves in.
The Black Lives Matter activists called the attack "an act of domestic terrorism" by "white supremacists" and took to the streets again Tuesday to show they were not intimidated.
Police said Clark died in a struggle with police responding to a domestic disturbance on November 15. Witnesses said he was handcuffed at the time.
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," Sutton said.
Mayor Betsy Hodges praised police for swiftly arresting suspects in the "abhorrent shooting" and said the city is "sparing no efforts to bring any and all those responsible to justice."