I need to find a behavioral therapist in or close to Longmont, Colorado for my brother... Can anyone help?

My brother has been acting very weird lately. He gets in trouble at school, he will not sit still, he randomly yells things, has a horrible temper etc... I want to find someone who can tell my family what is wrong with him and either help fix it through therapy or putting him on medication. He has been on meds for ADD before but he stopped taking them, and they never helped with his violence. I don't completely know what I need to find so any help would be appreciated.