Why my crush and his friends laugh at me when I pass them without looking at them?

I don't like him so much but he is a cute guy. Last week, he saw me staring at him and he started to flirt with me. He may think I like him so he told his friends. When I pass them, he and his friends started to laugh at me in insulting way
Why my crush and his friends laugh at me when I pass them without looking at them?
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