Pulling up your pants is not a reason to get shot. Other jurisdictions don’t seem to have the same problem of shooting people who have already surrendered.
EDIT: You are right, that was a poor example for this situation. I can't reply to you, but the only point I'm trying to make is that it is very easy to see this situation after the fact. But I would imagine it is next to impossible to verify some of these facts in real time with confidence.
Back in reality the police shot a man who already surrendered and was unarmed. This would be a war crime on a battlefield, but the police are held to a lower standard.