Why does he ignore me after saying we should hang out?

I've known this guy since 10th grade and am now a senior. I admired him from afar and so I finally told him I had a crush on him. He admitted having a crush on me too so I was happy for a while till he started ignoring me. He said we should hang out sometime before we graduate so I became all stoked ready to hang out. I ask him about prom to which he started ignoring me. I asked him why but he won't answer me. I'm really confused but I know there are more fish in the sea...maybe I should try something else? Thanks for reading.