His emotional communication and regulation skills are likely delayed. In the absence of options, there’s only one response to anger, a primal one. Work with him on building social and emotional skills. You can use programs like The Incredible 5-Point Scale and The Zones of Regulation to help with this. I like social stories a lot for younger kids too.
ADDitude Community Moderator, Parenting ADHD Coach, Podcaster & Author, Mom to teen w/ ADHD, LDs, and autism