What do you think someone's responsibility should be if they fall asleep on the job with a disastrous result (for example killing people)?

The other day my family was discussing the recent Thanksgiving weekend Metro North train accident where the train engineer (driver) fell asleep and the train rounded a turn going over 80 mph and derailed, killing 4 people and injuring many more. In addition, the track got screwed up which affected the commutes of tens of thousands of people who use that rail line to go to and from New York City each day.

The train engineer apparently fell asleep. Drug and alcohol tests were negative.

My family members were discussing the engineer being defended by his union and/or attorney and the implications of falling asleep on the job. Would it be acceptable for a surgeon to fall asleep on the job and do something terrible to a patient on the operating table? Would it be ok for a pilot to fall asleep and crash a plane?

These are not my thoughts, these are hypothetical situations that came up in the discussion.

I don’t want the question to be about this incident specifically, so I left those details out of the question. I want it to be more for general opinions – what should someone’s responsibility be for falling asleep on the job?