It really sounds like someone else is impersonating the guy you knew from childhood. I would be very, very careful. This guy could be dangerous. DO NOT meet him-- even in a public place-- unless he can absolutely confirm his identity.

Have you watched the show catfish? There are a lot of ways to do a little detective work online. Do a "reverse lookup" of this guy's e-mail address, phone number, physical address... or any other information you have. What name is listed? Look up his new name on google, linked in, criminal/background check websites, etc. See if there are current photos associated with the name/accounts. It really shouldn't be that hard to determine if this is the same guy or not.