Question about a fellow tenant in my apartment building.?

Ok, so here's the deal. My roommate and I have this guy living in our apartment who is an absolute wacko. He has displayed all sorts of weird/antisocial behavior ever since he moved in ... especially toward my roommate and I. I'm pretty sure he doesn't like us. This isn't my question, however. My question is this: Ever since he moved in we have been getting signed up for the most outlandish magazine/newsletter subscriptions. Now we're about 99% sure that he is doing this to piss us off. Is there anything possible way to prove that he's doing this? Should we contact the postal service? Any suggestions?