Since when is stopping a crime in progress vigilantism!?!
“any person who takes the law into his or her own hands, as by avenging a crime.”
Above is a difinition of “vigilantism”—I think it fits this situation.
Bingo.
“Since when is stopping a crime in progress vigilantism!?!”
It’s not, by itself, wrong, when the crime is in progress.
The big key here is to be sorry that the offender ultimately died from the fight, and move on.
However, holding grudges and continuing to hate the person after the act is being unforgiving,