As Starfire has stated the monster could be a spirit guide helping the child, I feel this is what the monster is too, but im no expert with this sort of thing.

The monster may also be a bad entity feeding off of the child's bad emotions such as its sorrow and fear, but I am not too sure.

Whatever it is just tell the child to not be afraid of it and to stay as calm as possible whenever he sees it.

You could also try praying for the child yourself, hoping to keep him safe and protected.

Keep us updated and I wish all the best for him.