Not a good idea to be calling for an assassin on a public blog. That's called conspiracy to murder.
Also, have you told this girl about your feelings? did this guy know? If you keep everything bottled up you can't expect the world to sit back and watch and wait for your balls to drop. So if you haven't done anything to be with this girl, who may or may not like you in return, don't resort to illegal methods of revenge in public. It's simply bad form.
ohbombuh
Just figure out a way to convince the girl that the guy's a pervert, and you'll never have to worry about her getting stolen. I suggest telling her you saw him trying to drill a peep hole in the girls' locker room wall.