Short answers, pulled from the story.
Chapman cited several grievances: anger at Lennon's lavish lifestyle, which he saw as contradicting Lennon's message in "Imagine"; Lennon's 1966 remark that the Beatles were "more popular than Jesus"; and Lennon's song "God," in which Lennon said he did not believe in God or the Beatles. Chapman also described a desire to become famous and said he had modeled his worldview on Holden Caulfield, the protagonist of The Catcher in the Rye.
Chapman shot Lennon in the archway entrance of the Dakota apartment building on the Upper West Side of New York City on the 8th of December 1980. He fired five hollow-point bullets from a Charter Arms Undercover .38 Special revolver; four struck Lennon in the back and shoulder. Lennon was rushed to Roosevelt Hospital and pronounced dead on arrival.
Judge Dennis Edwards Jr. sentenced Chapman to 20 years to life in prison on the 24th of August 1981, five years less than the maximum sentence of 25 years to life. The sentence included a stipulation that mental health treatment be provided during his incarceration.
Parole has been denied 14 times. Chapman first became eligible in 2000 and under New York state law receives a hearing every two years. His next parole hearing is scheduled for February 2027.
Chapman regarded J. D. Salinger's 1951 novel as a personal manifesto and reportedly wished to model his life on its protagonist Holden Caulfield. On the morning of the shooting he bought a copy, wrote "this is my statement" inside it, and signed it "Holden Caulfield." At his sentencing hearing he read aloud a passage from the novel rather than speaking his own words.
Chapman is held at Green Haven Correctional Facility in Beekman, New York, in Dutchess County. He was transferred there on the 30th of March 2022, from the Wende Correctional Facility in Alden, New York, where he had been held since the 15th of May 2012.