[Useless]

It's perfectly legal. I would suggest that you have him brutally beaten, if I was the type of guy who thought that pounding some useless motherfucker's sick skull into the pavement solved things.

Call the police. Though they may not be able to do much, they may find it interesting enough to stop and chat with the guy. You need to start taking charge of the situation and show this guy that you will not be intimidated that you will not be his willing victim. If you don't have the support network to help deal with someone menacing you in this fashion, you need to move.