Teresa screams at Thomas to listen to her: all he needs to do is reach inside the Grievers' skins, and inside there's a handle switch that will kill them.
Hmm, sounds disgusting.
Thomas frantically runs around to the pods, shutting off Grievers and killing them. He gets to the fourth pod, but it's just climbing out when he reaches it. A pair of scissor-blades swipe at his head, and he ducks. Luckily, he finds the switch, and it, too, dies.
But there is one last Griever. It spins forward with machines in its belly, then slices through a bunch of people with its blades. More deaths; more carnage.
Thomas yells at Minho to get everyone into the maintenance room, while Thomas distracts the Griever.
Teresa tries to help, but the Griever starts sucking her face into its blubbery skin, suffocating her.
Thomas finds a pipe nearby, then gives it a shot—he smashes the Griever, then plunges his arm into its flesh. It starts to stab him, but he finds the switch and it turns off. Phew.