When You Reach Me by Rebecca Stead shared by srsam

In sixth grade Miranda and Sal know their street smarts; they know who
and what to avoid- and one of them is the man on the sidewalk corner
who always hides his head under the mailbox (Quack a.k.a. "the
laughing man"). But after Sal gets punched by a bully he ends his
friendship with Miranda; and Miranda needs to make new friends (she
meets Colin and Annemarie). Strange things start happening to Miranda
and her mother; the apartment key gets stolen from it's hiding space,
and she starts getting secret notes no one should read. The notes tell
her something tragic is going to happen and that she may just be too
late.