Guys, If A Man Is Taken or Not Interested, Why Does He Glance At Me?

Hey there, gentlemen!

So, I kind of have a strange question about this person I work with, who appears to be very shy but super intelligent. He has been working with us for 3 months, just starting after he transferred to our floor from another position.

A few weeks ago, I made the mistake of finding him very attractive, and so, I asked him if I could buy him a cup of coffee sometime. He took a few seconds to respond before telling me that he is currently involved with someone so he had to politely decline. When he left the office where we were talking, he looked back at me and then hurried towards the door to his own office.

Since then, he had avoided speaking to me, he keeps his head down mostly but, a few coworkers including myself have noticed him taking small glances or staring at me when he passes our office. At first, I thought I was paranoid, until someone else mentioned that he had done it once or twice. Today, he did it a few times, getting caught by my coworker and refusing to look directly at me when I had to ask him a work related question.

Is this strange behavior? Why is he doing this? It is making me absolutely insane and I feel like I am going mad. It's frustrating and not fair if he really is involved with someone. Help?
Guys, If A Man Is Taken or Not Interested, Why Does He Glance At Me?
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