Why his friends stare at me and laugh when they see me? Why does he act like that?

Anonymous
Well, I stared at a guy twice and he started to do the same. I didn't like him, it was only to ogle (discreetly) him, as people do when they see attractive people. But I forgot him and I moved on because he didn't interest me more than that.
But, recently, I saw his friends talking while I was walking, and, another time, one of them was kind of laughing. I didn't like that because I don't even know them and didn't do anything to stand out.
The weirdest was that the guy I ogle a long time ago didn't say or do anything. He didn't laugh.
One day, I was walking (again!) and they were starting to climb the stairs when, I suppose, one of his friends saw me and they stopped climbing, turned their bodies towards me even if I didn't look at them at all. They didn't move until I moved. I did my best to ignore them all.
And, when the guy is alone, he smiles (kind of half smile or smirk?) at me, what I don't understand.

Please, is there someone who is an expert about guy's behaviour (guys themself?) ?
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+1 y
I need your help, pleeeeeeease
Why his friends stare at me and laugh when they see me? Why does he act like that?
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