Who wrote Samuel's prophesying? Helaman 13:39

Who wrote Samuel's prophesying? Helaman 13:39

There's a long discourse included in the book of Helaman that seems to be directly quoting an ancient prophet named Samuel the Lamanite. I wanted to know how it came to be that we have those words. Somebody must have written them down. Was the hearer experiencing it firsthand? I don't know. Was it an abridgment? I also don't know, but I suspect not just because of the word choice with the first person pronouns.

Answer:
We don't know.