Guy's Behavior

I'm confused. Why would a guy go out of his way to walk near or past you, but won't speak to you?

I work in the seafood department, and there is a guy who works in deli. Seafood and deli are pretty far apart in the store I work at. Lately I've noticed this deli guy comes over to the seafood department an awful lot. He's also been staring at me from the deli department, and when we make eye contact sometimes he will hold it. Other times he looks away.. I've asked my friends who work in the same department if the guy walks past or into the department when I'm not there (I only work there once or twice a week now). They said he never does and that it's weird he's been doing that. They say he only does it when I'm there.. My friends have also said they have noticed him watching me. I've tried talking to him but his energy is pretty intense and I get nervous and just walk away. A few times I've actually talked to him but have only gotten small talk. I know he thinks I'm a hard person to read (overheard him say it once). He hasn't really tried to talk to me, so I'm confused. So what is his deal?
I'm confused. Why would a guy go out of his way to walk near or past you, but won't speak to you?
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