The bottom line fact is, cops are very poorly trained and are as often as not amped up on adrenaline, which can be just as bad as any other drug on ones judgment, and they are shooting, too often, too soon, and killing people who were simply not that much of a threat.
Let me throw a " some" in front of cops, there. Sure they are amped up on adrenaline, depending on the behaviour of the person involved, whether they had to chase them, the area they make the stop and time of day/night, there are things which indicate some stops are going to be more of a problem than others. No two ways about it. Some do shoot too soon, or do not correctly assess the threat. My experience has been that the police here have generally conducted themselves professionally, with reasonable caution.
But then, I call them "officer", and have kidded with the youngsters in the family often enough about being on a first-name basis with all the police force (that being "Officer") and that they can be, too, if they just remember that. It sets a different tone than "M*****f****r!", and chances are that whatever was an issue will be the only issue, solved calmly, no gunplay involved.
They are told to speak calmly, respectfully, and to refrain from profanity.
Hmm. Civil, nonthreatening behaviour works. Hoodathunkit?