K.T.
How is his communication skills at home and in general? Aside from throwing fits, can he communicate with words appropriately? If he has problem communicating with words appropriately, he may have a language delay that is causing frustration. If not, it's behavioral.
My daughter will be 4 in 2 weeks and up until recently would cry a lot instead of using her words. Hers is not a language issue, it was just behavioral.
If it's behavioral, talk to him about being a BIG BOY! Praise him when he does act like a big boy. Talk to him about how good he talks, when he does, and that you like to hear him use his words.
If you think he has a problem with his langauge skills, get him a language evaluation IMMEDIATELY!! www.slpsinc.com