I do quality assurance/programming for a living, and volunteer in emergency management. I do find myself making assumptions, or generally doing the "it won't happen to me" thing. Its human, and it only takes a moment lapse of being anal about things to beget tragedy. Everyone always second guesses people who are involved an accidents and thinks those people are "dumb", but it can happen to all of us.

My thoughts are with your friend, and yourself. Stay safe.