This is horrible. I have same. When I hear someone dead in some way,my mind suddenly created a scenary of me dieing in that way. Like falling,drowning,hit by train and everything possible. This is so horrible,that makes me hard to breathe and usualy my heart get's to beat so fast,that it pains. This is because,we starting to feel like we are dying right now,and that fear can be the same like it would actualy be.