Clarence Ray Allen was born on January 16, 1930, in Blair, Oklahoma. He grew up in a small town in southwest Oklahoma and claimed to have Choctaw heritage. At the age of 17, Clarence married Helen Sevier. He met her a year earlier while they were working together in the fields. 

In 1974, Clarence Ray Allen was involved in a plot to rob Fran's Market, a supermarket in the Fresno area. He arranged for a burglary with the help of his son, Roger Allen, and others. During the plan, they stole door and alarm keys from the owner's son, Bryon Schletewitz. The robbery took place while Schletewitz was distracted. They managed to steal $500 in cash and $10,000 in money orders.

After the burglary, a girl named Mary Sue Kitts, who was Roger's girlfriend, told Bryon about Allen's involvement. Schletewitz confronted Roger, who then informed Clarence. In response, Clarence decided that Bryon and Kitts needed to be silenced. He called a meeting with his associates and voted to kill Kitts because they feared for their safety if they disagreed.

Allen ordered Lee Furrow to carry out the murder of Kitts. Furrow attempted to poison her, but when that failed, he strangled her instead. He then disposed of her body in a canal. Kitts's body was never found. Eventually, Furrow confessed to the murder and named Allen as the mastermind.

While in prison, Allen conspired with another inmate, Billy Ray Hamilton, to murder witnesses from his previous trial. On September 5, 1980, Hamilton and his girlfriend went to Fran's Market, where Bryon worked. They killed Bryon and two other employees, Josephine Rocha and Douglas White, using a sawed-off shotgun. Two others were wounded during the attack.

Allen was later tried for the murders and conspiracy to kill witnesses. He was convicted and sentenced to death. In 1982, he received the death penalty after evidence showed he had a history of orchestrating violent crimes.

Years later, despite attempts to appeal, his death sentence was upheld. He was executed by lethal injection on January 17, 2006, at the age of 76. Allen's final meal included traditional Native American dishes. His execution marked him as the second-oldest person executed in the U.S. since 1976.