How do you tame a kids bad temper???

Oh my goodness I have a child that thinks any time he doesn't get what he wants from another kid he needs to hurt them physically. Oh and please don't think I'm letting him get away with this but my goodness where does that temper come from??? When he was in school he asked a student to see his paper and when the kid said no he scratched him with a pair of scissors. When he gets in trouble if we send him to his room he throws a tantrum and will attempt to destroy the room. I'm being patient and talking to him and making him understand that that's not acceptable behavior but in the mean time it's almost scary that he may really hurt someone. If he keeps it up I think Ritalin is going to be in his future. ;)