He was resisting arrest. He was speaking so he could breath. I see no indication the officer intended to injure him. The video says he died of a heart attack not of strangulation. By definition if you are talking you are breathing since speech is nothing more than modulated breath.
I still no force being used until he refused to comply. I still see him being release once he was secured and I still see his non compliance as the reason force was used. I do think the officer should be disciplined and mostly fired but I don't see disregard for human life.