It might be helpful to find some books to read with your son about his angry feelings, and what he can do with them. One is:
When Sophie Gets Angry--Really, Really Angry...
by Molly Bang
A children's librarian at your library or your pediatrician can suggest other books...
With my kids, I used to sing an old Mr. Rogers song---"What do you do with the mad that you feel? Do you jump up and down?" etc.
It's OK to have angry feelings---everybody has them---but then you have to teach them how to deal with them, and safe ways to express their anger. It's scary for them, too.

