Why did he stare at me?

My college is big, but I always see the same people on campus. I sat next to this guy in the library like 2 weeks ago. We glanced at each other and when I got up to get my papers from the printer, I saw him looking at me. I walked passed him today on campus. I didn't look at him the whole time because he was staring at me. We made eye contact. I think he is cute, but I am not the type of girl to talk or say hey to guys I don't know.