Moves too fast to be tracked at night

He began working his way down, but he froze as he saw some of the men down below firing on each other. Men were dropping right and left, and some of them were vanishing into the ground. He would see shadows moving around the camp sights, so swiftly that he never actually got a good look at them. They would vanish and a moment later a man would disappear, dropping through the ground and causing some of the men to fire wildly at the ground and at each other.

***

Hell