Allen Blackthorne's death behind bars was certain. It was only a matter of how long the Texas millionaire who arranged his ex-wife's murder in Sarasota would live.This week, the 59-year-old died in the federal prison in Terra Haute, Ind., 14 years after he was handed two life sentences, according to the U.S. Bureau of Prisons website. No cause of death was listed.The Blackthorne case made Tampa Bay headlines for more than three years. Sheila Bellush, often referred to as the "Quad Mom" for the quadruplets she had with her second husband, was found with her throat slit in her Sarasota home in 1997. Two of her then-2-year-old children were found crawling in the 35-year-old's blood. Bellush and Blackthorne divorced in 1989 and had a bitter custody dispute over their two daughters. Bellush moved to Florida from San Antonio, Texas, in 1997, and six weeks later she was killed by hit man Jose Luis Del Toro Jr.Blackthorne, who made his money developing a medical device that stimulates muscles, played golf constantly, including rounds with gambling buddy Daniel Rocha. Prosecutors say Blackthorne asked Rocha to arrange the killing.Rocha approached San Antonio golf course bag boy Samuel Gonzales to find someone for the job. Gonzales asked his cousin, Del Toro. For his part, Rocha was offered a partnership in a golf course development, maybe even a $400,000 loan for a sports bar. The hit man would be paid $54,000 plus a bonus if Blackthorne regained custody of the girls, who had been adopted by Sheila Bellush's second husband.Del Toro, a 24-year-old former high school football player from a small town 90 miles southwest of San Antonio, drove to Florida for the killing. He shot and stabbed Bellush at the home she shared with her husband, Jamie Bellush, their quadruplets and the daughters she had with Blackthorne, Daryl and Stevie.Del Toro pleaded guilty to murder charges and was sentenced to life in prison in Florida the same day a Texas jury convicted Blackthorne. Rocha, whose testimony helped convict Blackthorne, was given life in prison. Gonzales was sentenced to 19 years behind bars. During the trial, Blackthorne admitted he once threatened to kill his ex-wife because he thought she was a negligent mother, but he denied arranging her murder. At his sentencing hearing in San Antonio in November 2000, Daryl Bellush told a judge her father had "given me the ability to hate.""The day I'm happy again is the day that my mom is alive," Bellush, who was 15 at the time, told the judge. "Unfortunately, that's not happening. So I guess I'll compromise. He can spend the rest of his life in jail and die there."Then I can go out and celebrate."Information from the Associated Press and Times files was used in this report.