The shooting triggered widespread protests in Chicago, a city already struggling with soaring murder rates.
Video from a dashboard-mounted camera shows McDonald walking away from Van Dyke, who aimed his gun at the teen as soon as he arrived on the scene.
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.
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. It is extremely rare for police officers to be tried and convicted of murder for shootings that occurred while they were on duty.
Before Judge Vincent Gaughan dismissed them for the day Thursday evening, jurors requested a transcript of testimony from former Officer Joseph Walsh, Van Dyke's partner the night of McDonald's death.
Prosecutors have argued that the video shows Van Dyke used unnecessary and excessive force, including firing shots after McDonald had fallen to the ground. Defense attorney Dan Herbert told the judge that Van Dyke's tardiness was because he was dealing with a threat to one of his daughters.
The prosecution quickly countered that Van Dyke's account was not corroborated by video evidence of the shooting. Police brutality and shooting cases have long brought unrest and protest into communities of color - a fact that suggests the city could reach a fever pitch if Van Dyke walks free.
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.
The jury was also given the option of finding him guilty of second-degree murder, which would indicate the mitigating factor that the killing was not premeditated, but that Van Dyke showed obvious disregard for the consequences of his action.
They opted for this lesser charge and also found him guilty of 16 counts of aggravated battery with a firearm - one count for each bullet he fired.
"I thought the officers were under attack", Van Dyke said. That's the criteria for second-degree murder.
"Someone needed to arrest Laquan McDonald, not stop him with a hail of gunfire", McMahon said in his closing argument on Thursday.
The crowd frequently chanted "guilty" as they would stop at major intersections and in front of Trump Tower along the way north of the Chicago River on Michigan Ave.
The verdict is the latest chapter in a story that has led to the police superintendent and the county's top prosecutor both losing their jobs - one fired by the mayor and the other ousted by voters.
"The people's cup has run over with these police violations of people's rights", he said. "Should this occur, it may create potentially unsafe situations around the city".
As jurors began deliberating, the Chicago Police Department canceled days off and put officers on 12-hour shifts.
It would appear that Van Dyke's sentencing is a change in the narrative, that hopefully leads to more accountability in the nation's police departments.