Why does he make eye contact then ignore me?

There’s this guy that started staring at me and I started staring back and since then we have been making eye contact but we hold it until I look away but when I make too much eye contact he ignores me but when I do the same he stares at me again when I’m not looking and always looks for me in the hallways. He gives me an intense look
Why does he make eye contact then ignore me?
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