Boss's bad temper

I have been with this company for about a year now. My boss has only been in his position as Executive Director for about 2.5 years. He was Deputy before and got promoted unexpectedly, which partially explains his unprofessionalism in dealing with his position. What's more, he's fairly young and very immature (wants to be friends with everyone and makes fun of others to be part of the gossip group). Some of our team members left, from what I could tell it was mostly because of the way he treated them.

So far I have witnessed 3 separate incidents where he has lost his temper with his employees or some of my peers. My office is very close to his so I can hear anything that goes on, but of course he yells so I wouldn't miss a thing even if I tried. It happened again today and it is starting to make me feel very anxious. So far he has not lost his temper with me but he cannot take any form of criticism or he gets very defensive off the bat.

I am very worried about any type of interaction with him, because I don't want to be his next victim and I like my job aside from dealing with him. I find myself being overly nice to him in trying to avoid any type of confrontation, but that cannot possibly be the solution, right? How should I handle this? HR knows about this situation but their hands are tied. Any tips?