He's staring when I wasn't looking, but doesn't seem like he's interested?

i caught this guy staring at me in a few occasions, where he immediately look away when I look at him. but when was I near him, I can see he's trying hard not to look at me, as if he's not interested. but I can see him staring or looking from corner of my eyes when I wasn't looking. why he did this? because he thinks I am eying on him as well? he never smile to me or say hi.
He's staring when I wasn't looking, but doesn't seem like he's interested?
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