If a person is resisting with non-deadly force, there are options an officer has to convince the person to comply.
When a person is in custody on the ground, I can’t see where pinning the person to the ground by applying pressure to the neck with a knee for a length of time sufficient to kill, i.e. 5 minutes, is justifiable in anyway, especially if the person is saying that they cannot breathe.
There is no way to defend what happened in this arrest in my opinion. I do not support any rioting either. Charge the men involved, send it to court.
It probably killed him because he was already in poor health. In any case, these cops picked the wrong moment. carelessly apply force.
These cops should have mastered the technique of speeding to the call at 25 mph with sirens blaring. In the unhappy event he was still there when they arrived...give him a stern warning.
Let society enjoy the world of crime they clearly want.