Guys don't like rejection. Probably the majority of guys wouldn't put themselves up for rejection unless they knew there was a good chance of it not happening. How does this happen? He finds out that there's interest coming from you.
Most guys would rather not have to face the possibility of rejection if they don't have to. My friends tend to stare a lot and get nervous when the one they like talks to them. If they sound like they are more caring than before they might have deeper feelings for you.
I know this from experience, so please do not make a big deal of it publicly, it is really awkward for the guy for a long time. My experience with that was not only a huge let down but my friends got on me about for a few months.