My friend, who I recently asked out, said he would just prefer to be friends. I was cool, and continued on with my life.
However, all of a sudden he starts ignoring me, becoming snippy when I try to ask him anything, even say a simple hello, so eventually I stopped responding to him to. Did I do the right thing? Why would this happen all of a sudden? Should I talk with him again?
That is so weird because this happen to be to I think, he feels it is awkward for you to be around him or maybe he is not feeling you and don't want to let you know.
I think he's scared now that he knows how you felt. He probably doesn't get or even see that you moved on and are totally cool with being just friends. This is his (very immature and lame way but way normal for your age group) of pushing you way so he you don't fall for him and stop liking him.
I can't say you did the wrong thing by telling him, I actually applaud and admire you for having the courage to do so. I'm older than you and I could never be that brave. I can say, however, that next time test the waters first before asking a guy out. Make sure he likes you then ask him out or drop hints here and there so he'll ask you. You'll never be 100% sure if he likes you because men are the most confusing species in the world (not to mention a lot are flirts by nature) but at least you'll go into it with 80% certainty.
If you value his friendship and consider him such a good friend that you still want him in your life, wait for a chance when he's alone (guys get stupid when they're with friends) and ask him if everything's cool with you. Let him know that you're not into him in that way anymore and enjoy his friendship. Then keep on with your life and let him decide how he wants to treat you. If he continues to act like an ass, forget him. His loss and you don't need him, you probably have many other friends who treat you with respect.
Also, don't let this one guy hold you back or scare you off from approaching guys. Not all of them will reject you or act like immature babies when they don't see you as more than a friend.
Gosh, this is EXACTLY what happened to me a month ago. In my opinion, he's thinking that you're not over him or something like that. I acted the same way as 'he' did. Speaking from my own experience, he's acting hostile because he needs time away from you.
He's thinking that after he rejected you, you should be avoiding/keeping yourself away from him for some period of time.
I cannot say that whether you did the right or wrong thing since every guy is different in personality and how they think.
After you stopped talking to him, when you do start to talk to him in the future, he may either ignore you or warm up to you. : )