I'm white, and I've been the victim of physical police brutality not once, but twice in my life. This was with white and latino cops. Both times it was completely unprovoked. I offered no resistance. I was completely cooperative and polite. I asked the cop once, "why are you doing this?" He just smiled. He enjoyed it, and could get away with it. A sadist I guess.
I don't think what I said above fully applies to Chauvin. He looks up, and can see there's someone a few feet away recording him, and he doesn't stop. This sorta makes it scarier in my mind. He's supposed to be a trained professional, and he seems to think torturing a handcuffed man is normal! Apparently the three other cops do, too.
I think it's one factor why he was charged with 3rd degree murder, which lacks intent. No one intends to kill someone on camera. Police have gotten very used to heavy-handed overkill. You see it when they send in a large SWAT team to serve a warrant on some non-violent person. You see it in how roughly they treat people of all races.
ETA: Since posting this, I just learned they upped the charge to 2nd degree murder. Can't find what that's based on, but it sounds like the kind of stupid overreach prosecutors often do. Although I suppose the most hated man in America will go down for anything they choose, whether it's right or wrong.