The police were responding to a 911 call from a woman who said that her boyfriend, Jacob Blake, had been violent to her and had stolen her car keys. The police identified Blake as someone who was additionally wanted for sexual assault, for trespassing, and for domestic abuse.
When the police arrived, the woman who had called them told the police that Blake had kidnapped her child and was trying to steal her car.
Blake approached the police, concealing the knife as best as he could, and he refused to drop the knife when the police did see it.
The police tried to use non-lethal means (tasers) to subdue Blake, but they didn't work.
Blake attacked police, briefly holding one of the officers in a headlock.
After the police shot Blake, all the blacks began saying that the shooting was "unnecessary," that the account of the police was a big bunch of lies, and that the police were the "real" aggressors. Blake's family hired Ben Crump, the sleazy black attorney who represented the families of black thugs Trayvon Martin and Michael Brown, to represent them in their civil suit against the police, in the hope of winning what has been called a "black payday."
And the blacks in Kenosha rioted, of course. The behavior pattern is well-studied: the blacks first announce that they will assemble to protest peaceably, then, after enough of them have gathered, they become a violent threat to persons and to property, beating and killing law-abiding citizens, breaking car windows, setting fire to businesses, and stealing everything that they can lay their hands on.
Sympathetic (and similar) black protests-cum-riots were held in New York, Minneapolis, Los Angeles, and Atlanta.
Although at first the involved officers were placed on administrative leave (26 August), while the wimpy, pandering Wisconsin Governor Tony Evers denounced excessive use of force by police, the prosecutors eventually (January 2021) decided not to charge them with any criminal offense. Probably because they couldn't make any such charge seem even remotely plausible, given the circumstances.