Why does he keep staring at me?

[Harry]

There's a guy in the year below at college and for the past few months he's been staring at me quite a lot. On the bus, he sits a few seats ahead but at the odd time he'll look back and glance at me, but when it's just us two on the bus (because we get on a few stops between) if he sits in front of me, he'll turn his head round a bit and stare at me, and then I'll look and he'll quickly look away, then he'll do the same a few minutes later, but sometimes we just stare at each other until I look away. Also, at college in the lounge the other day, he was sat in front nearby and kept staring at me while he was with a group of girls. The thing is, I don't know why he is doing this, but I thought for a bit that it might be because he thinks I am stalking him because we see each other everywhere: I added him on Facebook and then his friend pointed at me one day and laughed while I was with people so I confronted the guy about it because he was there but he said he didn't know why his friend did it, but after that his friends never really acknowledged me. Then I followed him on Twitter because I really did like him, but he never followed me back so that's when I was kind-of put off him (and unfollowed). But ever since he didn't follow me back (before Christmas break), he's been doing more staring and especially in the past week he's been doing this looking-at-me-on-the-bus-and-quickly-looking-away stuff, and even when walking to lessons if we see each other he'll stare at me and I'll stare back, but it is more of a neutral stare.

He is really shy and never really talks, and my friends thought he fancied either me or one of my close girl friends, but one of my friends had to persuade him to talk to her by text although he told him he liked her and he messaged her once but text her one-word answers, but whenever I was with with her, he'd stare at her, but now that's stopped and he only stares at me since I followed him on Twitter. My friends mainly think he fancies me now, but he does tend to look at them a lot, but not as much as he looks at me, but my close girl friend thinks he might just want to be my friend or admires me (a bit weird). He's met up with a guy (an old friend) before, who I know, so I know he must be at least bi but in the closet because nobody knows about it, yet I just need to know why he is staring at me and do you reckon it's because he likes me?
(P.S. nobody knows I'm bi and I never know how to talk to him because it would be really random to)
@Danny I'm just wondering how could I ask him on an outing without it being weird because if I only talk to him once (from asking to use his phone for example) it would be random if I asked him if he wanted to do something hahaha he probably thinks I'm a weirdo