Hi, I'd like to help you with your question.
This person may want to see their doctor first to rule out any medical condition that could cause them to act out. You are correct about the sleep issue. Lack of sleep can make it harder to control your feelings, especially stronger emotions like anger. The doctor may recommend a sleep study to get to the bottom of why this person is not sleeping. The doctor could also prescribe medications to help induce sleep until the cause is found.
Does this person use alcohol or drugs? This could adversely affect their moods and cause sleep disturbances. Steroids in particular can cause extreme anger responses.
You can help the situation by remaining calm when this person becomes angry. It is hard, I know, in the face of such a frightening and strong emotional response, but the more calm you remain, the more likely this person will mirror your reaction and calm down themselves. Take a deep breath and see if he will do the same. Do it until you feel he is calming down.
Would this person consider anger management classes? That might be a good start in helping him learn techniques on controlling his anger and learning better ways to channel his feelings.
Also, would he consider counseling? This is also an excellent way to learn ways to cope and it would also help him get to the bottom of the anger, as long as any physical cause is ruled out. Have him talk with the doctor for a referral or he can search on line for a therapist at http://therapists.psychologytoday.com/rms/.
Does he have any spiritual beliefs? Sometimes, people can find solace in their faith. There is also a lot of support through church programs. Talking with a pastor can help in that they can provide ways faith helps with anger issues.
Here are some books that may help as well:
Rage: A Step-by-step Guide to Overcoming Explosive Anger by Ronald T. Potter-Efron
Beyond Anger: A Guide for Men: How to Free Yourself from the Grip of Anger and Get More Out of Life by Thomas J. Harbin
Angry All the Time: An Emergency Guide to Anger Control by Ronald T. Potter-Efron
You can find these books on Amazon.com or your local library may have them for you.
If at any time you feel this person's anger gets out of control and it is directed at you, leave immediately. Also, keep a cell phone on you with emergency numbers on speed dial in case you cannot get away quickly. I don't want to scare you, but it never hurts to be prepared.
I hope this has helped you,