Some schizophrenia symptoms described at:
http://counsellingresource.com/distr...renia-symptoms
More professional than layperson terminology, but you can get the gist.
There are all sorts of disorders though. From what little you've described, I think it *could* be that, but it could be so many other things that I wouldn't even bother speculating on the diagnosis. Talking to his parents, very tactfully, sounds like a good idea.
If he's exhibited signs of paranoia, be especially careful, as talking about him behind his back, or even confronting him personally, could fuel his paraoia.
Also note that this and other disorders can vary over a huge range from minor to severe. I know someone with a mild case of schizophrenia, treated with medication for years (they've been getting better and better, with fewer side effects), and he holds a regular job and relates to people pretty well (not common, but like I said there's a range). Conversations can take abrupt turns, and people meeting him think he's a little weird, but it's not obvious that he has this disease.