Guy's Behavior

Why does this guy look at me in a certain way?

It's like his eyes glow... there's just something in his eyes. He doesn't really smile, nor does he look away. I mean he has smiled once, but it was when I passed by him and his friend, so I couldn't tell if he was smiling at me or not. Maybe he was smiling at his friend, but before that I held eye contact with him until he passed by. Whenever I see him, there's this look in his eyes, and it catches my attention. I don't really see him looking at other people, but one time, I walked past him while he was sitting, and I don't know what caught my attention, but for some reason I ended up looking at him, and he was just sitting there leaning his face on his hand, directly staring at me. It was so weird. It's like a look I can't forget for some reason. A look where his eyes seemed weird. Like they glowed. Like there was something to him. And he was just looking at me and as I looked over at him, he didn't stop or turn away, he just looked at me in a weird way. Could he have just been looking at me in a weird way like that, because I didn't see an email? Sometimes I send emails to people and forget to check if they and then I see them later and respond again. But later on, in the afternoon I realized he replied. But that doesn't matter. What could be that strange look in his eyes?
Why does this guy look at me in a certain way?
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