There have been more than one incident in specific types of accidents, but the onces that come to mind the most are:

Motor vehicle accident - My husband was killed by a teenager in a head on collision.

Fire - A very good officer friend burned to death in his police car responding to a call and was alive at the time.

Suicide - I have had more than one friend in emergency personnel commit suicide, and a very close friend did so while we were in high school.

Murder - My cousin was murdered in an alley on his way to the store to get my Aunt some milk. He was 8 years old and lived on a small reservation. Shot in the head for about 4 dollars.

Other accident - I used to work for a commercial airline, and very close friends who were flying standby and co-workers died in the crash of one of our aircraft.

As a result I never hang up the phone or leave someone while angry or telling them I love them, no matter what.