My dad is a retired cop. He was shot at, run after with a knife, and gotten into many altercations with violent perps. His opinion based on the video footage he's seen is there is a deep cultural problem in current law enforcement. He can't fathom why anyone would kneel on a man's neck for 8 minutes, or push a non-threatening elderly man to the ground, or shoot any unarmed person in the back as they are running away even if it was following a physical confrontation, and that none of these go unpunished.
I had a long talk about it with him and he told me there were times where things got heated and he got emotional and he felt tempted to go hard on the person who attacked him, and this includes the time he arrested a young man and was swarmed by a mob of his friends who surrounded his cruiser and they threw a large stone through the windshield with the nearest help being 40 minutes away. He didn't start the car and mow them over, or pull out his gun and started shooting. Instead, he released the guy he had arrested (after having obtained his identity), and negotiated his way out. They did go back to arrest the kid along with several of the people who attacked my dad, but nobody got hurt. He says too many cops don't use their heads anymore and react impulsively, and don't take to heart their social responsibility. Peacekeeping and law enforcement goes beyond carrying a badge, a gun and handcuffs. It's also community outreach, and a deep concern with public safety that includes the people you are intercepting for an arrest.
Cops nowadays are protected by their union, as they should be, but they are overly protected which gives them a feeling of invulnerability with the law. He does say the presence of so many video recording devices does complicate the situation, but it can also help them. The problem is we are catching more and more cops being in dereliction of duty and then the act is going unpunished. Police reform is needed.