The prevalence of guns is surely largely responsible for the large number of people killed by the police. Every time they pull someone over, they're aware that the person could conceivably put a gun in their face out of nowhere, which means that they're constantly on edge. Any sudden movements and they've grabbed their gun and shot 5 bullets before they've even thought about it.

I remember watching a video about a year ago about a guy (black, obviously) who was at a petrol station when the police asked him for his license. He reached into his car to get it and the policeman fired about 5-7 shots at him out of nowhere, despite the guy shouting that he's just getting his license. I don't think the guy suffered serious injuries, but I don't think the police officer approached the situation with the intent to shoot the guy. He was just in fear for his own life and overreacted quite ridiculously.

Edit: Here it is:



At least one shot fired while he had his hands in the air.