So, one of my friends at my school has a stalker...?

And when I say stalker I mean he fallows her everywhere. I'm seriously thinking about shoving him up against a locker and beating the hell out of him. The only problem is is he's like 5 feet tall and scrawny as hell. I'll feel bad. Should I do it though? It's been going on for like 3 years... Him stalking her that is...