Hi G.,
Many kids who appear to have these bad tempers actually have not developed proper coping skills. Many times this can be related to health. There are two ways you can address it, one using floortime play techniques (Stanley Greenspan). When it happens, you have to try to step in his shoes "Wow, Ethan, I can tell you are really mad", moving to different techniques of "Lets hit this pillow together and see if it makes us feel better" (you demonstrate). Etc. After the episode is over, see if you can discuss it allowing him to lead the conversation as much as possible. Holding and brushing are two techniques that you can try during the episode as well.
Next, is where you are probably going to need to go as well. Many, many children are suffering from a low immune (causing low grade allergies or digestive sensitivites). I would highly recommend trying a couple changes, the first of which to remove milk based products or any products containing casein (milk protein). After 2-3 weeks, you can also research going gluten and casein free.
I know this sounds a little out there, but you will not believe the behavior changes in children that need this.
There is a book called Healing the Childhood epidemics by Bock, MD you may wish to read. Your son cannot control the behavior because it stems from a lack of ability to cope and calm. Don't forget how that would make you feel. Think about how you feel when you have a cold and you have something very important to do, but just can't do it. At least you know you will get better and do it, he just feels bad because he is not good.
If you struggle with the behavior while you are working on the health side, there is a fabulous group called www.floortimeatlanta.com. They are fabulous floortime therapist and have tons of stategies for helping him.
Best of luck, J.