So here's a wild idea: cops should never kill anyone for any reason in any circumstance. A cop killing someone represents, at best, a failure to correctly deescalate the situation. Any cop who kills anyone should be immediately banned from being a cop ever again AND put on criminal trial (no internal investigations). If they are found not guilty of murder, then they can go get another job doing something else. But no one who has ever killed another person should still be a cop.