Do they teach them to put their entire weight on the side of the man’s neck until well after he passes out?
I've studied martial arts for over 40 years. We learn many techniques that have a goal of "compliance". When we hit that point, we can then back off ever so slightly but maintain the hold so that if the training partner tries to escape, we can immediately apply just a little pressure and they instantly become very "compliant" again. We can hold them that way for hours if needed, safely under our control.
I have no idea what this cop did or what his intentions were, but you'll never know by watching a video.
I hate bad cops as much as anyone, but right now this guy is an unknown based on my personal MA training.
Maybe the medical examiner can determine if loss of blood flow to the brain was the cause of death. I'll wait for the results before judging.