The passenger of the truck said the driver was like "this isn't the trail" (they were on the slabs and it is really easy to get off track if you don't know it especially at night) so the driver stopped while his truck was flexed up on a rock. The driver took his seat belt off opened the door and as he stood on the slider it went over. I don't know if that is exactly what happened, but that is what I thought I overheard the passenger telling somebody.
That is a fully shitty situation. It really makes me think twice about making sure my truck is really stable before taking my seatbelt off and getting out.