But the jury found Van Dyke guilty of second-degree murder and other charges. Jurors found him not guilty of official misconduct.
Authorities in Chicago were anxious that unrest might occur if a not guilty verdict came back. It's the first time in half a century that a Chicago police officer has been convicted of murder for an on-duty death.
The Chicago Marathon is due to be staged this Sunday, placing police and the city under greater strain.
The city prepared for the possiblity of widespread protests but for many of those who've been campaigning for the past four years there was celebration rather than upset. Mr. Van Dyke testified in his own defense that Mr. McDonald advanced, pointed a 3-inch knife toward him and attempted to get up off the ground-none of which was shown in the dashboard footage.
Van Dyke faced a count of first-degree murder, one charge of official misconduct and 16 counts of aggravated battery, one for each shot fired.
Though he was originally charged with first-degree murder, jurors were instructed Thursday that they also could consider second-degree murder.
City officials resisted for months releasing a dashboard camera video that showed Van Dyke fire 16 shots at the teenager, who was walking away from officers.
The deadly encounter unfolded when officers came upon McDonald, who had a knife, and called for an officer with a Taser to respond to the scene. PCP, known as Phencyclidine, is a dissociative hallucinogenic drug known to trigger outbursts of violence in users. So, if Van Dyke gets the minimum for each count, he'd serve six years for all the battery convictions.
All of this was deemed necessary even though, as WBEZ's Natalie Moore noted on Twitter, there hasn't been a full-fledged riot in Chicago in 50 years, and while plenty of activists took to the streets after the 2015 release of the video showing Van Dyke shooting McDonald, the marches were overwhelmingly peaceful. Seven are white, three are Hispanic, one is Asian-American and one is African-American.
The 12-person jury reached a verdict just one day after beginning deliberations.
The reaction in Norris Friday was muted: the roughly three dozen people standing around the TV nodded or quietly sighed in relief after the verdict was announced.
Miller thinks Van Dyke testifying in his defense made a difference in him being convicted of second-degree murder.
A judge has decided against taking a Chicago police officer on trial for murder into custody for being late to a court hearing.
Van Dyke was charged with first degree-murder in the October 2014 killing, a charge that requires a finding that the shooting was unnecessary and unreasonable.
In the aftermath of McDonald's death, three other police officers - including Van Dyke's partner on the night - were charged past year with attempting to cover up the shooting, to which they pleaded not guilty.
Defence attorney Daniel Herbert called it "unprecedented" for an officer to be charged with murder for doing his job to stop an armed offender. "This isn't", he told the jury in his closing argument.
The aftermath rallied the city's politics and led to significant changes within the police department.