We know from references to the truck driver’s journal that Pervis was part of a group of long-haulers that kept the roads cleared and stocked with boxes of trade-able goods.
But was she part of that group before things went kablooey, and when did his death happen in relation to Sarah and Wendell stealing the truck?
It probably involves Pervis’ philanthropic trek prior to his death, though we don’t yet know whether his current handler was responsible for his lethal arm bite(s).
That can be assumed, considering she’d faked a mile marker sign and used Pervis to dispatch Quinn, who then became her new pet to mark up and weaponize.