Why's he denying it?

This guy (21m) and I (21f) take the same finance class and he'd always ignore me at uni but after seeing me all dressed up at a wedding he began to take interest. At the wedding, he kept stealing glances and while my friends and I were walking, he stood ahead of our trail and kept staring at me as I walked closer and closer, until I passed him. My friends saw this and thought it was creepy, they told me to avoid him but I politely tried speaking to him. However, he rudely denied it and said I was imagining things- umm what?

Why's he denying it?
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