Flirting

Guy friend rejected me but still stares and looks at me? WTH?

we have known each other for four years, and were good friends, he would always tease me and call me pretty, and loved to mess with me, but since i have told him that i liked him, he has stopped and we have drifted apart.,
---- 3 months before I told him he whispered that he had a crush on me and I pretended I did not hear him, and then he got nervous and backed out , he is also really shy..-----
---its been 9 months since i told him that i liked him, and he told me that he only likes me as friends but every single time he sees me he just stares and does not look away sometimes..
--For example i was walking to class and he was on the other side of sidewalk, it was kind of leveled up and he saw me, he was about to cross the tree, and he backed up, leaned back and stared at me with no expression for three seconds and went on walking to his class. i saw this all from the corner of my eye..
--- if we ever pass by each other he looks at me from the corner of his eye also...
-- so my question is why do guys stare at the girl they rejected?
Guy friend rejected me but still stares and looks at me? WTH?
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