Wasn't your dad the boss of him before? Maybe you just need to make sure he understands you're the boss of him now.
um... who? he's a chick I sold as a new hatch and got back from the person who bought him a couple months ago... my dad has nothing to do with chickens, except for eat them and their eggs. (besides it'd be hard raising chickens while camping across south texas in the winter).
and talking with the person who had him, she had seen signs of aggression as well, which is NOT tolerated. period. so yeah he might be trained out of it, but I don't want it there to begin with. so he's on the short list.