Finally a diagnosis

My 4yo son that I adore so much was finally diagnosed. I have jumped through hoops trying to find out what is wrong with this child. First major incident he bit me and drew blood on my side in front of my brother's counselor. My brother has ADHD and has home visits with his counselor. She had me take him to get evaluated. A few weeks ago there was another incident. My 2yo is autistic and goes to therapy. I usually take my 4yo, but I couldn't this time. My brother's case manager with Baycare had came that day for him. Long story short I come home from therapy and my mother tells me Angel, my 4yo, threatened her in front of my little brother's case manager. He told her he was going to stab her with a knife and kill her   Needless to say she immediately assigned herself to his case and had him put in therapy asap...they said he has ADHD....

I would double check this diagnosis. There are many things that can cause violent outbursts in children. Is this the only symptom your child has?