Karr reportedly made a yearbook entry in 1982 that has similarities to the ransom note found in JonBenet Ramsey's Boulder, Colo., home after her body was found on Christmas day, 1996.
"Though, deep in the future, maybe I shall be the conquerer [sic] and live in multiple peace," the entry read, according to the Rocky Mountain News.
The ransom note concluded with the single-word exclamation "Victory!" and was signed "S.B.T.C." Investigators are looking into whether those initials may stand for "shall be the conqueror." Other explanations have been proposed for those initials, including that they were a reference to the Subic Bay Training Center, a now-closed naval base where John Ramsey was stationed.
John Karr was an "uncontrollable" and "possessive" child who would throw tantrums until he got what he wanted, McCray said. But, he said, John Karr was "smart as hell, talented and sharp as a tack."
McCrary gave John his first job as a teenager -- loading and unloading furniture at a Georgia warehouse. McCrary said John quit on his first day, saying his arms hurt and that the work was too tough for him.
McCrary said John later talked his father into selling one of the family's rental properties and going into the car business.
"They started buying cars, fixing them up, and selling them," McCrary said. "He found a DeLorean and said 'Daddy, I want that. And his daddy said, 'All right.' They got a good price for it."
Referring to John's diverse and unusual talents, McCrary recounted a story of John once single-handedly dismantling and re-assembling the DeLorean.
"When John wanted something, he was totally focused on getting it," McCrary said. "He had an unbelievable mind."
John was also musically gifted and played 12-string guitar expertly as a teen, according to McCrary. One summer in Georgia, during his brief marriage to Quientana Shotts, he came to a Fourth of July party and sang the "most beautiful harmonies you've ever heard" with local country legend Sam Allen, whose stage name was Billy Autumn, McCrary said. The duet so impressed Allen that he told the young man he wanted to sign him up for a record contract on the spot.
Allen and McCrary got on the phone that day and contacted Baker Knight, an industry legend who wrote Ricky Nelson's hit "Lonesome Town" and whose songs were recorded by Elvis Presley and Frank Sinatra. A record deal was discussed over the phone. It never materialized.
John met Shotts in Hamilton, Ala., and he married her when he was 19 and she was 13, Shotts' parents, Larry and Melissa, told ABC News.
"I've never seen two kids more in love in my life," McCrary said.
But Shotts' parents were opposed to the marriage. McCrary said John had a lengthy battle with Shotts' parents over his relationship with their daughter. The more the parents resisted the couple's plans, the more defensive and possessive Karr became.
At some point in the relationship Shotts left him, McCary said, and Karr "put up one of his great efforts to get what he wanted."
"It was the talk of Hamilton,'' McCrary said.
Eventually, Karr won her back, but the marriage ended in nine months.
John's second marriage -- to Lara Knutson -- was also marked by heated opposition from her parents.
In 1989, when he was 24 and living back in Atlanta, John married a pregnant, 16-year old Knutson.