LITTLE FLOWERS OF SAINT FRANCIS OF ASSISI, Chapter 17
The little child in this story is what most caught my attention. He reminded me of the story of Samuel when he was a boy. But interestingly, when I think about the two stories, there is more of contrast than of parallel. Samuel didn't recognise God's voice, and the priest eventually figured out that it was the voice of God, and told Samuel what to do when he heard the voice again. In this story, the boy knows, and the Brother Francis tries to let him sleep.
More of a parallel is the similarities between the vision recounted here and the time Jesus and a couple of His desciples were on a mountaintop and Jesus was visited by Moses and Elija. In both cases, the witnesses were cautioned to silence for the time being.
And one more comment, about the child falling to the ground as if dead on seeing the vision. It's beyond my personal experience, but relatively commonly mentioned that someone fell into such a state upon or after a vision. Then Brother Francis picking him up and - as the story mentions - carries him like Jesus carrying a lamb. This is the kind of story where if we let ourselves reflect upon it, it's two stories, one about Saint Francis and a little boy, and another about Everyman being carried as a little lamb by Jesus, and we can see ourselves in either story.