I can't believe after all the dickhead Police Officers I have come in contact over the last year or so I am going to do this but here goes:
98% of cops don't ever shoot their guns in the line of duty, in their entire careers ever. So who are you showing it's not acceptable to kill an unarmed civilian? The guy that killed the black guy with a knee? He was involved in several shootings, that should tell you all you need to know. Telling him anything would be a giant waste.
The real problem is the age old problem for all armed militia's, armies, and police forces, what do you do when you witness unacceptable behavior. The Asian officer should have pushed that dick off or the very least stopped it. That's the behavior you need to correct. Again that excrement is the worry of every army save for the Nazi's and the Gestapo.
The other problem is weeding out the guys like the knee guy, the guys that go looking for trouble. He has like 19 investigations against him, several for shooting his gun. If PO's in NYC hardly use their guns, why would a Minneapolis cop need to be involved in several officer involved shootings? If you fire your gun more than twice, there's probably better lines of work for you. You should be put on mandatory desk duty.