It's bad to attack someone.
Amy saw a man physically fighting with a woman on the sidewalk in front of a jewelry store.
Amy wanted to save the woman from being hurt by the man.
Amy called the police when she saw the scuffle on the sidewalk.
Amy jumped on the man's back and started choking him while the woman ran away.
The man got his watch back from the police who arrested the woman for trying to steal his watch.
The man was badly hurt by Amy even though he was the real victim and the woman was trying to steal his watch.