Stalker or secret admirer?

I once glanced over at this guy (a distant friend) and smiled at him. Ever since, he began this thing of locking eyes with me for a few seconds, but since he wouldn't talk to me even when I tried msging him, I dropped taking interest in him.
He still began hiding behind a door/wall to stare at me as I spoke to people but since it was only for a few seconds, I ignored it. However, he then began watching me from a distance and if I get up to walk away, he'd literally bend his body over and continue watching me as I move around the place. I mean he only sees me at occasionally, but whenever he does, he watches me from a distance for up to 1-2 minutes straight at a time. This length of time made it unsettling, so I once hid behind a wall for a few seconds to avoid it, but even when I stepped out, he was still there, watching me. Is this stalking or does he think he's just being innocent about it? I'm 24 (almost 25), he's 28 and it's been going for 5 years.
Stalker or secret admirer?
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