I am so sorry that you have lost your friend and boss, but, and listen to this: IT IS NOT YOUR FAULT!!!!!
I have lost pretty much my whole family to heart attacks, and there is not one thing you can do to prevent them if they are predisposed. Did you control his diet or his life (or her) outside of work? Unless you were in total control of their life 24 hours a day, you couldn’t have prevented it. And the stress of blaming yourself will not help you with Grave’s.
Mourn, it is natural, but don’t blame yourself. You and your boss and the family are in my thoughts and prayers.
Mitakuye Oyasin
Val
