system
A chat on subreddit /r/NoStupidQuestions
human
Training alone won't fix the problem, the primary issue is culture. Police culture views the public as an active threat to them and they treat the public accordingly.  The popularity of noted hack David Grossman's perverse "Killology" is indicative of cop culture. Grossman used to and probably still does go around telling cops that if you kill someone you'll have the best sex of your life that evening. Note that Grossman never killed a single person in his military career. US cop culture also encourages them to take the slightest delay or mistake in compliance as an insult to their authority and that violence is an acceptable way to address that. It's like the old Japanese practice of kiri-sute gomen only they try their best not to punish you if it wasn't justified and the victims don't have the right to defend themselves. The Daniel Shaver case is a good example, he did his best to play the cop's sadistic game of Simon Says but made a small mistake which cost him his life.  


Also there are states and local departments in the US that require 2 year associate's degrees or 4 year bachelor's degrees for their officers. It doesn't help. Minneapolis has required either a 2 year degree or 5 years of police/military experience for ages and we all know what they did to George Floyd.
gpt
Underated comment.