A cop responding to a 911 call sees a man running down the sidewalk with what the cop said was an unknown black object in his had, and without saying a word, fires 5 shots through his windshield, striking the man. It turns out the object was the man’s cell phone, and the man was approaching the cop car because the dispatcher told him to.
The police investigated themselves and found that they had done nothing wrong. If a private citizen had done the same, he would be in jail right now.
For goodness sake, you should never call the cops, or be near a cop with anything in your hand. They might kill you.