That is a valid concern! And it's the main reason I'm generally against vigilantism, since I've grown up. (Also, I edited my comment while you were replying - I didn't mean to rugpull you, I just realised I wasn't articulate enough in my point about the trolley problem applying).

But, murder is still murder and this guy is probably going to get caught and put on trial, and punished. I think most people who wouldn't risk it before this won't risk it now, and certainly not for petty grievances, but if someone's situation is dire enough...