NEED SOME HELP WITH THE CATCHER IN THE RYE BOOKINGS?

OK MR HOLDEN CAUFFIELD IS THE MAIN MAN AND HE IS A PROTOGONIST BUT IS HE THE ONLY ONE? I THINK HIS ROOMMATE IS ANOTHER AND HIS STORY IS VERY BENEFICIAL TO PHOEBE AND THE CHESS PLAYER WHO HE LIVES IN LOVE AND THIS A GOOD BOOK MY QUESTION IS WHO IS THE SERIAL KILLER AND WHY DOES THIS BOOK MAKE EVERYONE KILL EACH OTHER ANSWER AND GET 10 POINTS YOU LITTLE NUT HEAD