What does this mean if a guy stares at me for 5 seconds? and has done is before?

He looked at me in a intense kind of way I don't really know how to explain it but it just turned me on. He was riding past on a bike so I think that's why the eye contact didn't last long and he wasn't that far away. it lasted 5 seconds.

but I know him but not really I don't know how to really explain it but my parents know his parents and his Younger brother and sister. but I don't think he knows me; he's in his late 20s like I think maybe 26 i don't know but he's tall; and really attractive.

he has done this before ; one time I was walking not exactly towards him, is say near him and he looked straight into my eyes and I did the same for a few seconds but I couldn't handle it anymore and looked away.(I kept looking away and back at him a few times)
What does this mean if a guy stares at me for 5 seconds? and has done is before?
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