The question is what happens to the people who kill without that being the appropriate response. What happened to the police officers who killed those 41 unarmed people? Is there a detailed public report I can read about what happened, including any disciplinary or management measures that were taken? How about the others - who's ensuring that it was an appropriate and proportionate response to the danger? Can I read their report? Is there a body which makes recommendations to the police on how to ensure that are less likely to happen? And the mere presence of a weapon doesn't always make it an appropriate response, especially in a country where there is a legal right to own a weapon. We're well aware than internal investigations don't work, and that external investigations only sort of work.
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.