Killer in the school

You pick up the nearest book to you and hurl it at the killer. It crashes into him which knocks him to the ground. Seeing the advantage your friends rush forwards. The hooded killer gets up but can see he is outnumbered. He dashs off into the corridor. A white piece of paper falls out of his pocket as he goes. You pick it up. It simply has a number on it. 1579. You are puzzled by this and decide you must explore the tunnel.