i am not incredibly qualified to answer this as i have little experience with children, but i know from personal experience that it sounds like it could could be an anger management issue. i was diagnosed with ADHD when i was a child, but even before this, i used to be extremely aggressive, so my mother had me see someone about my "anger management" issues. i was not a "bad kid," and also recieved high grades in school (and i've turned out just fine, by the way! on the shy side if anything, haha) but i used to hit my sisters, be very impulsive, and throw things. it could even be mild bi-polarity (him "having two personalities") but it sounds, to me, more of an anger managment issue. i'm just throwing it out there

hope everything works out!!