That's what causes the problem. Police apologists imagine circumstances that justify their abuse, and are absolutely certain that's what actually happened.
If there was a video, I wouldn't imagine. I'd watch and see what happened.
Well you saw the video of him robbing the store and assaulting the clerk moments earlier but that doesn't bother you?
Edit since I can't reply:
At least you didn't say "Police murder innocent black child" so that is a start. His actions moments before make the cops story more likely to be true.
But whatever crime he committed, extra-judicial summary execution seems a bit harsh.
Treating criminals this way doesn't make crime go away. And it breeds an attitude among cops that harms people who never committed even petty crimes.
Even if there was a video of him murdering someone that wouldn't justify killing him on the spot. It would justify arresting him and letting his punishment be decided in court.
You say this as if people are looking for an excuse to riot. No one wants a riot, it's bad for the participants, the police, the community, and the local economy. The only winners are looters.