We always need to know why when something like this happens. Especially when a loved one is taken in their prime. This happened to me when my wife died in her 30's after a long illness. I can give you some advice. But, no one can tell you exactly what you need to be at peace. I can see hints of what God had planned for me and maybe all of the trials have been necassary to get me ready for the trials to come. Now, I don't see the majority of the population being tried as much as me; so, that is another of my "why" questions.
Search your heart for what God has planned for you, then try to follow his will to the best of your ability. You will experience small and great victories for the rest of your days.

Don