I witnessed a head on collision once. On the way home from work after closing the store up. I pulled over, and immediately checked to see if anyone was injured. Both parties where ok, just shaken up. One person was pissed because he just bought his car the day before. I didn't view the actual impact, I don't remember the reason why. After I made sure both parties where ok (I don't think anyone had a cell phone on them, this was 8 years ago), I got back in my car and left. I probably shoulda waited for the cops, but it was getting near midnight and I still had a half hour drive to get home.
I cannot believe that this person just drove around the accident though. How inhuman do you have to be to watch a car get t-boned hard enough to kill someone, and then just drive around it like it was some minor annoyance.