(my current theory as to why the US military is more enlightened than US police is (a) they normally operate in situations where they have to win hearts and minds, and (b) "up or out" gets rid of bad apples)
For what it's worth, I have colleagues who have gone through police academy. It's 2 years here, which may correlate with the <1 per 10mm rate on: https://en.wikipedia.org/wiki/List_of_killings_by_law_enforc...