What is with my guy friend?

He is 19 and I am 16 (we met at school last year) Since he goes to college a few states away, we email each other a lot. Whenever we see each other in person (even back when he went to my school), he always used to stare at me and he never talked unless I came up to him. He is an outgoing person and seems to only do this around me. We both love art/drawing, and we have a lot in common. When I said bye to him once, I gave him a hug, and he didn't seem nervous about hugging me or anything. Why does he act like this towards me?