To put things bluntly, this guy is probably a turd. What kind of worthwhile person would do that to anyone? It's probably best that you avoid him for...pretty much forever. Guys like that aren't worth your time or your attention.
We can never be sure what happened, but I must say it's rather odd that a guy just randomly started ignoring you. But from what I read, it sounds like he wasn't even a good guy to begin with. If he easily told you that he liked you and not to mention he did that online, I just can't help but feel a bit skeptical about all that.
So seriously, just ignore this guy. You deserve better.