The question in one sentence is merely part of the movie; I don't think I watched it all as I was very young.
There are about four or five of these tall monsters who have claws, and they attack people, seemingly fleeing a train that the monsters have derailed as the train crosses a desert. The people flee into some of the caves nearby but it appears that the monsters live in these caves, as they are quite large. One monster grabs one guy with his claws, and the guy screams (naturally) "I don't wanna die!" The monster either eats him or dashes him against the rocks. Much mayhem, other people screaming and being attacked. That's it.