He was also found guilty of 16 counts of aggravated battery but was found not guilty of official misconduct. Jurors were told Thursday they had the option of convicting Van Dyke of second-degree murder, which is probationable.
Van Dyke, who shot McDonald 16 times, was one of several officers on the scene but the only one to use his gun. The defense built their counterargument around the video not being enough evidence to accurately depict the scenario for Van Dyke.
McDonald was carrying a knife when Van Dyke fired 16 shots into the 17-year-old as he walked away from police.
But Van Dyke, who testified in his own defense, tearfully told jurors that he felt threatened and that the video, which was taken from the side, did not show the scene from his perspective.
"This is an emotional time for our city, and many activists are calling for people to take to the streets regardless of the outcome of the trial", wrote Principal Brianna Latko of St. Ignatius College Prep, a private school in downtown Chicago, in a letter, according to the newspaper. "Cases, such as Laquan McDonald, Mike Brown, Alton Sterling, [Sandra Bland] and Philando Castile are brutal illustrations on why we need a clear documentation of facts when citizen-encounters with police turn deadly".
"[His] eyes were bugging out".
Van Dyke told the jury Tuesday that McDonald's face was expressionless - "his eyes were just bugging out of his head" - as the teenager kept "advancing" on him, holding a knife.
"I could see him starting to push up with his left hand off the ground". That case, which also involved an officer shooting someone with a knife, ended in conviction in 1970.
"It wasn't the knife in Laquan's hand that made the defendant kill him that night".
Mayor Rahm Emanuel and Police Superintendent Eddie Johnson, in a joint statement, appealed for calm. A Justice Department investigation carried out in 2016 and 2017 found that the Chicago Police Department routinely used excessive force, often against the city's black and latino communities.
The city saw protests after video of the shooting was released in 2015, and activists have been planning how they might react to a verdict.
Van Dyke is now being held in custody.
In anticipation of possible unrest, the Chicago Police had put the entire force on 12-hour shifts and cancelled any planned days off. They attend different schools.
The verdict will be announced at 1:45 p.m. Appointed special prosecutor when then-Cook County State's Attorney Anita Alvarez recused herself and her office from the politically charged case, the career prosecutor strikes a far calmer, less flashy figure in court than Herbert, who routinely verbally spars with the judge.
However, anti-police fliers posted around the city and posts on social media had led police to be watchful in northwest and southwest neighbourhoods where many police officers live. They gathered in front of the mayor's home, on Lake Shore Drive and even on two lanes of the Dan Ryan Expressway to call attention to police reform and what they charged was a cover-up from city hall.