My friend & I were at a party about a week ago and I met a guy who said that I was cute and wanted to add me on Facebook, so I let him. I didn't think anything of it, but as the party progressed, he kept clinging to me, talking to me and eventually asked if I wanted to go out with him when we got to know each other better. I told him maybe, because he had said earlier on that when his girlfriend dumped him he became suicidal for a bit and I wasn't sure what else to say so suddenly.

He seems like a really nice guy, but I'm not interested in him at all and there's also a bit of an age difference (he's 15 & I'm 18) and while I could try to avoid him forever, we have a few mutual friends.

How do I let him down easy?