If the cop had shot him in the head you would see just as much twisted logic justifying it.
He had drugs up his anus. He had COVID. He was foaming at the mouth from the start. He was behaving erratically from the start. He wasn't complying to repeated instructions. The cops called paramedics long before he was on the ground. He DIED while he was in police custody. The cops didn't kill him so your example is using false logic.