Conversation so far:
who wrote the notes in when you reach me
In When You Reach Me, a homeless laughing man sends Miranda notes.
Who is the laughing man in the book When You Reach Me?
A homeless man lives on the corner of Miranda's street. She calls him the laughing man for his tendency to laugh without cause.
Why did the laughing man in When You Reach Me write notes to Miranda?
The notes, whose writer claims to be coming to Miranda's time to save a life, offer three signs of the truth of the messages.
Does the laughing man succeed in saving a life in When You Reach Me?
Sal runs onto a street right ahead of an oncoming truck. The laughing man kicks Sal out of the way, sacrificing his own life for Sal's.

Question: Who is Sal?
Self-contained rewrite: Who is Sal in When You Reach Me?