Yes, this is a position I use extensively in martial arts but it is INTENDED to cause pain for compliance, & people can tap out.

If it is used in regards to establishing control then after control was achieved keeping it applied is either incompetence or willful aggression. https://twitter.com/CatchWrestling/status/1265632620572016640

So at a bare minimum, what the officer did is manslaughter and at worst - 1st degree murder.