Before the apocalypse, this was a fuel depot.
During the onset of the apocalypse Dwight and Sherry came into the nearby forest in an effort to avoid the undead to no avail. They eventually reached the this place and took one of the trucks from here. With that truck, they doused the forest in gasoline and then went on to burn the forest to the group, in hopes of killing every single walker in the vicinity. In the process of doing this, they killed Carla and Delly who were hiding out in a greenhouse located inside the forest.
As they keep moving, D lays out a plan to find "Patty" and then leave immediately. He describes how he and Sherry burned the entire forest with the walkers in it. He then explains that they joined up with a community, thinking naively that they would rebuild society together. Daryl argues that they should let him go, but D refuses to listen. Shortly after, Daryl suggests that they're making a mistake. D holds him at gunpoint, and angrily demands that Daryl tell him whether he poses an immediate threat, and whether he should be killed. Daryl says no.
They arrive at a gated parking lot, full of walkers. "Patty", D says. "She's gone." The women begin to panic, and Tina faints. As they tend to her, Daryl grabs their duffel bag and runs back into the woods, evading gunfire from D.