How do you explain??

How do you help a child deal with the death of a friend? For that matter, how do you help them deal with it or understand it? Yesterday, my step-son, Trevor, found out that his best friend had passed away. Not only am I trying to help him cope, my son, Chase, (who is 8 months younger) is struggling with it also. This is the 2nd death that Trevor has had to deal with in the last 5 months. The day before Mother's Day, Trevor's mom's ex-boyfriend took his own life because she broke up with him .... he was in his mid 30's!!! Trevor seems to have dealt with that a little bit better than he is with his friend Kyle's passing. Kyle apparently had really bad asthma and earlier this week, while playing with his dog, he collapsed in his front room. After rushing him to the hospital, they discovered that his lung had collapsed. As of right now, he is still "with us" physically, but has absolutely no brain activity. They currently have him on life support because he wanted to help other kids, so the parents are donating his organs. Personally, I think that is an extremely selfless act and I applaud them. Knowing that while they can no longer help Kyle, they can still help countless other people. Trevor likes to talk about Kyle alot right now and I don't blame him. It's so hard though to see the hurt in his eyes as he talks about him. Chase came in to me last night while I was trying to go to bed, crying his eyes out saying that he couldn't stop thinking about Kyle. Chase didn't even know him. Chase is struggling with the fact that Kyle was so young and doesn't think that life is fair. In his eyes, he doesn't think that anyone should die ....... EVER. How do you make someone his age understand when you don't understand it yourself? We didn't even know Kyle and it hit me so hard, I had to leave work and go home. I just sat at my desk crying and wishing that there was something I could do for poor Trevor. My biggest fear is that he will start to have a hard time getting attached to people for fear that they may die on him too. So far, he's doing ok. I'm just literally hoping and praying that he stays strong and continues to be the happy little boy that I've always known.