Hello,
this is not an expected side effect of stimulant medications, and not at all typical behavior for a child. I would contact your prescriber immediately to report this behavior. I would also recommend you ask your primary care provider for a referral to a psychologist for a consultation. Your son desperately needs help managing his moods, and a psychologist can help him learn better coping strategies. Sometimes stimulants are associated with mood changes, so it would be helpful for you to find a psychologist who can consult with the prescribing physician to determine what is happening with your child.
Best Wishes
Rebecca Resnik
Hope you can find a solution to this problem, sounds very scary if you ask me.. My son has adhd but we haven't had any problems like this.