Shortly before 2 p.m., over a live news feed from the courtroom, the jury announced they found Van Dyke guilty for second degree murder and guilty on 16 counts of aggravated battery, one for each of the 16 shots that killed 17-year-old Laquan McDonald in October 2014.
The death of Laquan McDonald in 2014 triggered months of protests in Chicago and America's third-largest city is braced for more trouble after the verdict.
The encounter unfolded when officers came upon McDonald, who had a knife, and called for an officer with a Taser to respond to the scene.
Mr Van Dyke said he continued to shoot "at the knife" after Mr McDonald was on the ground, because he "just wanted him to get rid of that knife".
A South Side man was charged with threatening public officials inside the Leighton Criminal Court Building and over social media during the trial of Officer Jason Van Dyke, Chicago police said. The jurors, who did not give their names, said the veteran police officer did nothing to deescalate the situation that led up to the fatal shooting. Van Dyke said he fired in self-defense after McDonald lunged at him with a knife.
The panel of eight women and four men - seven of them white, one black, three Hispanic and one Asian - began deliberations Thursday afternoon.
The jury's decision will likely turn on whether they believe Van Dyke's testimony that he reasonably feared for his safety at the time. Van Dyke was originally charged with first-degree murder, aggravated battery with a firearm and official misconduct. The video, played repeatedly at trial, shows Van Dyke opening firing.
Ahead of the verdict, the city prepared for the possibility of the kind of massive protests that followed the release of the video in November 2015, with an extra 4,000 officers being put on the streets.
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In a joint statement, activist Carl Dix and philosopher Cornel West called Van Dyke's actions an act of "illegitimate violence" that the trial "reinforced".
Van Dyke, 40, was the first Chicago officer to be convicted of murder for an on-duty shooting in 48 years.
One legal expert predicted that Van Dyke will be sentenced to no more than six years total.
Van Dyke's attorney Daniel Herbert said Van Dyke's daughter's high school classmates were asking which student was the officer's daughter in order to attack her. The jury also had the option of first degree-murder, which required finding that the shooting was unnecessary and unreasonable. "At any point throughout that 20-some-minute rampage, had Laquan McDonald dropped that knife, he'd be here today".
"I'm really happy", Curtis said, "I really felt like if they had returned a not-guilty verdict I would have burst into tears immediately".
"It shows a perspective, but not the right perspective", he said.
The justice department issued a report a year ago that found the police had routinely violated the constitutional rights of the city's residents.
What Van Dyke saw "was a black boy walking down the street. having the audacity to ignore the police", McMahon said.