If a guy sees you and quickly looks away?

He saw me and quickly looked away when he saw me coming down the hall.. which is fine. But then he went into my coworkers office (he knew I was there) and we ended up talking and while we were talking, he looked at my face up and down. I’m not sure if he’s interested or not. If he isn’t interested.. why would he go somewhere he knew I would be at?
If a guy sees you and quickly looks away?
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