Considering they have a pact with the anotherother station, the route should be familiar to them. Briggs really confirmconfirms that saying "the helicopter" when talking through the radio with his base.
They approach the car with caution because the body outside the car: a man with a gun in thehis hand and a bullet in the head (he killed himself). Briggs looked inside the car and saw a woman and a kid dead in the same way (probably a family). The surprise could be because they don't expecteddidn't expect to find these bodies there, only andan empty car. This family should be "survivors" from the other station which reachreached that place but couldcouldn't walk anymore (e.g. too tired, no food, no water, no shelter).