Chapman, 57, went on to reveal that he had a list of six or seven potential targets, including Johnny Carson, Dame Elizabeth Taylor and actor George C Scott.
Chapman - who had waited for the singer to return to his apartment building before shooting him in the back of the head - had contemplated abandoning his murder plot when earlier in the day he met the British musician, who had signed his album cover.
He said: "It wasn't all totally cold-blooded, but most of it was. I did try to tell myself to leave. 'I've got the album, take it home, show my wife, everything will be fine.'
"But I was so compelled to commit that murder that nothing would have dragged me away from that building."
Chapman pleaded guilty to second degree murder and was sentenced to 20 years to life in August 1981, with the judge ruling that he must receive psychiatric treatment.
His most recent parole application was refused.
- Bang! Showbiz