Mark David Chapman (born May 10, 1955) is an American murderer who shot and killed John Lennon at the entrance to the Dakota apartment building in New York City on December 8, 1980. Chapman fired five times at Lennon, hitting him four times in the back, and read The Catcher in the Rye until he was arrested by police. He has repeatedly said that the novel was his statement. Chapman's legal team intended to mount an insanity defense that would be based on expert testimony that he was in a delusional psychotic state at the time of the killing.

On December 8, 1980, Chapman left his room at the Sheraton Hotel, leaving personal items behind that the police would later find. He bought a copy of The Catcher in the Rye in which he wrote "This is my statement", signing it "Holden Caulfield." He then spent most of the day near the entrance to the Dakota apartment building where Lennon lived, talking to fans and the doorman. Early in the morning, a distracted Chapman missed seeing Lennon step out of a cab and enter the Dakota. Later in the morning, he met Lennon's housekeeper who was returning from a walk with their five-year-old son Sean. Chapman reached in front of the housekeeper to shake Sean's hand and said that he was a beautiful boy, quoting Lennon's song "Beautiful Boy (Darling Boy)".  Around 5:00 p.m., Lennon and Ono left the Dakota for a recording session at Record Plant Studios. As they walked toward their limousine, Chapman shook hands with Lennon and asked for him to sign a copy of his album, Double Fantasy. Amateur photographer Paul Goresh took a photo of Lennon signing Chapman's album. In a later interview, Chapman said that he tried to get Goresh to stay and that he asked another Lennon fan who was lingering at the building's entrance to go out with him that night. He suggested that if the girl had accepted his invitation or Goresh had stayed, he would not have murdered Lennon that evening, but he probably would have tried another day.  Around 10:50 p.m., Lennon and Ono returned to the Dakota in a limousine. They got out of the vehicle, passed Chapman and walked toward the archway entrance of the building. From the street behind them, Chapman fired five hollow-point bullets from a .38 special revolver, four of which hit Lennon in the back and shoulder, puncturing his left lung and left subclavian artery. At the time, one newspaper reported that before Chapman fired, he softly called out "Mr. Lennon" and dropped into a combat stance. Chapman said that he does not recall saying anything and that Lennon did not turn around.  Chapman remained at the scene and appeared to be reading The Catcher in the Rye when the NYPD officers arrived and arrested him without incident. The first responders recognized that Lennon's wounds were severe and decided not to wait for an ambulance. They rushed the mortally wounded musician to Roosevelt Hospital in a squad car, but nothing could be done to save him. Lennon was pronounced dead by Dr. Stephan Lynn at 11:07 p.m. In his statement to police three hours later, Chapman stated, "I'm sure the big part of me is Holden Caulfield, who is the main person in the book. The small part of me must be the Devil."

Using a quote from the above article, answer the following question: Which book as he referring too?
The Catcher in the Rye