Why did he walk between my guy friend and me?

My coworker who I interact with for work purposes and who tries to get my attention outside the office did something quite strange.
There was a decoration competition going on and my guy friend and I went to check it out.
Now my guy friend is a really handsome person who's engaged recently, but no one knows about this. We are work friends and don't really interact much out of work.

This coworker sees me and him walk in side by and side. As we stand in one place and see around us, he walks really close to me even though there's space plenty in the corridor. Three people could stand side by side there. He sort of separates me from my guy friend by walking so close and he doesn't even go anywhere, he just returns the same way after we've moved on to different exhibits.

What is this dude's problem? I barely talk to him, even though our parents are acquaintances.
Why did he walk between my guy friend and me?
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