How does Mark manage to make his way back to the Central Shack in Chapter 4? What does he do afterward?

Screams fill the air, and Mark and the others drag Darnell’s body along. People fall to the ground, hit by darts, left and right. They make it to the Shack with Lana, where Alec is waiting with grappling hooks. Mark picks up a piece of wood to use as a shield as he heads out to help Alec do whatever must be done.