The author states, “Every movement in the grass was a lion stalking, every stillness a lion waiting to spring.” Explain the meaning of this and why Salva is thinking it.

Salva is overwhelmed by grief and fear. He clings to Uncle, looking around constantly. A lion took Marial in the night. He never would have walked off on his own, so the lion must have seen the small and weak boy and took him.
Uncle tries to comfort him, telling Salva he has a gun and they will soon be out of lion country. Salva despairs; he has lost his family and now his friend. The grass becomes an oppressive place.