When to play dirty?

I have a competitor that is using my full domain on his pages and in his URL strings. He is clearly sucking traffic off of my work, I tried emailing and asking for an explanation and asked if they would stop doing this tactic. No answer, what are my options? I don't want my domain damaged so I am hesitant to start tattling but what this clown is doing is complete B.S.
looking to hire the internet mafia to make his site sleep with the fishes

This is the internet, shit like that happens. Focus on your site and your money, rather than his.

Be careful with anyone who PMs you regarding with "internet mafia" offers after this post. In my experience, posts like this just attract scammers. Just order a couple of xrumer and scrapebox blasts from fiverr to the keywords he targets.