Here is an answer that was provided to someone who previously asked this question. (Answer written by Khushigargg).
"The weather was stormy and the winds were making hushing sounds and the trees were making eerie noise. It was dark in the forest and his torch was flickering.
It adds to the setting of story as in such an atmosphere people are prone to imagine things that actually don't exist due to fear and panic and that's what lead Mr. Oliver to imagine a boy with his school cap sitting and crying on a rock."
