After crashing and witnessing your squad getting mobbed, you have to flee the scene to avoid the cultists. Sprint in the opposite direction and keep running ahead until you spot a lumber mill. There’s a lone cultist there so crouch to remain stealthily and sneak behind him. There’s a pipe behind the large gear wheel so pick it up and use it to perform a Melee takedown on the cultist.
Pick up his handgun and check out the containers inside the lumber mill. There’s also a baseball bat on the shelf that you can pick up as a second Melee weapon. Continue forth and follow the trail. There’s a large bonfire ahead with two cultists warming themselves up. You should ignore them for now since engaging them will alert nearby cultists searching for you. Just follow the objective marker to the trailer house a short walk up the trail. Enter the trailer house to continue with the mission.
After the scene, you’ll receive a rifle from the marshall. Engage the incoming wave of cultists from the window. Make sure to take cover and heal up as necessary. Keep holding the cultists off until the marshall fixes up the truck outside. Once he’s in the truck, vault over the window and join him in the passenger side. (He won’t leave if you hop on the back of the truck)
Once he’s driving, you’ll have the task to shoot your pursuers. Prioritize taking out the drivers to crash vehicles. Don’t forget to lean back inside the truck to heal up or reload. Your ammo will be infinite during this sequence so don’t hold back in shooting and reloading as necessary. Make sure to fire rounds in short, controlled bursts for better accuracy. Do your best in shaking off your pursuers until your escape attempt is halted by a crash to the river. Mission complete.