This riddle has been around for some time on internet platforms such as Instagram, Facebook, and WhatsApp, and many people still argue over what the answer might be, as there are many possibilities. The correct answer is The numbers written on the calendar actually represents the months in the calendar whose initial letter represents the name of the killer. 1 = January [J] 4 = April [A] 9 = September [S] 10 = October [O] 11 = November [N] The killer is Jason.