Retrocop ...
Playing by the book would have been to press charges before anyone was assaulted. You allowed them to be assaulted, dismissed and able to be nicked by somebody else with no history.
If they had been charged then they could stop stealing. Other people would not have been stolen. Those people who has been would get their property back. And nobody would have been assaulted.
Instead, you went along with somebody else's summarily justice of an assault. The thief had a chance to steal again, with no history. And, luckily, nobody was seriously injured or killed, but may have been, with your implicit sanction to assault somebody - which is a crime.
This was (I hope not still) the problem with the police - thinking they knew better. Maybe some did, but not all, and not every time.