if a motorist tailgated you for miles then illegally passed you on the right when making a left turn, and then crashed into a tree....?

I would, forgiveness is devine, we all make mistakes and lose our temper from time to time. I would feel kind of bad if that person died.

I stop to determine if their were injuries.  If so, I'd help them get to a hospital then drive to the nearest police precinct & make a written report of the incident.  If not injuries, I'd just do the reporting.     

I would stop and take pictures then drive on...

Yes, it's an accident and you have to report it by law.

I would laugh my azz off and keep on going about my business.