My four year old son is always putting things in lines such as his hot wheels, all have to be in same direction. If they are moved or line is broken he will run to the corner and lay on the floor and cry. That is the only abnormal (for lack of better word) thing he freaks out about. Shoes thrown anywhere, toys all over floor, but cars must be organized? Today he had about 30 all lined out and came to one truck (he has hundreds of hot wheels) and started tearing up the line, when i asked him why he said he could not put it in order and he needed help. He does have delayed development in speech so communication is sometimes difficult. He goes to pre-k and his teachers love him say he is there best student. He plays with other kids but mostly by himself i think due to his speech.
By the way, I would assume that he is getting help for his speech? It should be free through your public school system. If not, the sooner he starts getting professional help, the greater the chances for him to improve will exist.
Finally, kids of his age don't problem solve well or deal with emotions well. They have to be taught. If you can show him better ways to deal with frustration, it would be great. I am guessing that maybe his speech problems make him feel like he can't communicate his frustrations?
There is an excellent series of books called the "learning to get along" series. One of the books is "Cool down and work through anger." Its aimed at the 4 to 7 year old and is meant to be read aloud to them. I think it might be worth trying as it gives alternate ways to deal with anger. It can be found here - http://www.amazon.com/Cool-Through-Anger-Learning-Along/dp/1575423464/ref=pd_sim_b_4
I hope this helps. He sounds like a neat kid!