Why does this guy always stare at me?

He stares at me A LOT; we always make eye contact; he’d be with his friends and he’d stop talking to them and step away and stare at me and my friends, wondering what we’d be talking about; he’d face his torso at me actually; when I walk by him, I’d look at him and catch him already looking at me, then he’d look away; when I enter the room, he’d be with his friends and they’d all stare at me and talk between themselves; or they’d stop talking and all look at me; when he stares at me, he has this serious look on his face or he’d be smiling; I can sometimes predict from the way he stares at me that he likes me; when I come down the stairs, he’d keep his eyes on me, and vice versa; when I walk by him without even looking at him; from the corner of my eye he’d turn his whole body and watch me as I walked by. This guy always notices me, do you think he’d stare if he was interested?