I'm so sorry for your friend. You will need to stick by him for many years.
One of my best friends up in Live Oak lost his son many years ago to a typical 'cross the fence' accident. The son was his eldest and 14 at the time plus he was suffering PTSD from Vietnam. It tore the family apart.
I wish that we could have been closer (by distance) and that I could have offered more support. If you have that opportunity, do it! You'll never regret it.