Mr Van Dyke was charged with first-degree murder, but has been convicted of the lesser charge.
Special prosecutor Joseph McMahon had told the jury that "under very special circumstances" a police officer can legally shoot a person but Van Dyke was charged with first-degree murder because "not a single shot was necessary or justified".
He was accused of first-degree murder and aggravated battery after police dashcam video taken on the evening of October 20, 2014, showed him opening fire within seconds of coming out of his patrol auto. When Van Dyke exited his police auto, he pulled out his gun and opened fire on McDonald nearly immediately, though the other officers on the scene didn't even have their guns drawn.
Surveillance footage of the incident showed Van Dyke appeared to shoot McDonald while the younger man was walking away from the officer.
Additionally, none of the other officers who were on the scene with Van Dyke in 2014 felt the need to fire their weapons, even after Van Dyke began discharging his own.
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. McDonald was pronounced dead at hospital. I see his left shoulder start to come up.
"It wasn't the knife in Laquan's hand that made the defendant kill him that night".
McDonald eventually fled to a Burger King parking lot and then into a nearby street, which is where Van Dyke and his partner arrived.
Other officers have also been charged, accused of covering up the shooting. 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.
Even the staff of Mayor Rahm Emanuel's administration were given the option to call it a day before the verdict, as police-reform activists swiftly massed in front of City Hall.
The Justice Department launched an investigation, concluding in a scathing report previous year that the department violates the constitutional rights of residents. Vic Mensa, who created the song "16 Shots" in dedication to McDonald's murder, also penned a message about the trial on Instagram. In addition, the presiding judge had reportedly filled the courtrooom with sheriffs to contain any outbursts when the verdict was announced.
"This case has been about exaggerating the threat and trying to hide behind the police shield", prosecutor Jody Gleason said in her closing statement.
"I'm glad they didn't just let him get away with it", said Armani Mitchell, a student at the charter school in the Bronzeville neighborhood.
The aftermath rallied the city's politics and led to significant changes within the police department.
The city has been on edge in advance of the verdict and city officials and business owners have beefed up security in expectation of protests.