In other countries like England & Wales, when a police officer seriously injures or kills someone, there's a formal investigation by the Independent Office for Police Conduct, an independent body at a centralised Government level with powers equivalent to a police officer for matters they investigate. They also usually provide public reports, for example, https://policeconduct.gov.uk/recommendations/police-response.... (Also note the limited use of force - two shots, one of which struck - and immediate care.) It's still not perfect, but it's a heck of a lot better than what the US does.
All officer involved shootings are investigated, but you take issue with the investigation being internal. If an independent investigation office was created, would you accept the results if the results still were the same? What group, would you accept results from in independent office from as not compromised or part of a pro-police conspiracy? Certainly not any Trump appointed office, no matter how seemingly neutral.
Also, circling back - even if the police only killed violent people, my personal experience is that their interactions with the community are pretty much always to threaten violence - except for their attempts to indoctrinate children into accepting their presence. I've seen police break ribs and knock non-violent, merely uncooperative, people unconscious, then fail to provide healthcare. They've harassed and threatened people attempting to film them, including taking details and arresting people who refuse to provide them. There was a spate where they arrested random people on my street for no stated reason, then released them just before they had to explain to a judge why they were arrested. Just because people don't die most of the time doesn't make them unaffected.
No-knock night raids should probably be considered a violation of the 2nd Amendment, among other things. Kenneth Walker was well within his rights to shoot the plainclothes cops breaking into his home in the middle of the night.