• The execution will be the fourth lethal injection in the state since October
  • Executions through lethal injection began in October after a nearly seven-year hiatus
  • Oklahoma put a hold on executions in 2015 after a botched lethal injection in 2014

The state of Oklahoma is set to execute Thursday a man convicted for his role in a quadruple murder in 2005.

The execution of Gilbert Ray Postelle, 35, will take place through a lethal injection at the Oklahoma State Penitentiary. The execution will be the fourth lethal injection in the state since October, when the death row lethal injections restarted, following a nearly seven-year hiatus.

Gilbert, who was 18 at the time of the crimes, was sentenced to death for his involvement in the Memorial Day 2005 shooting deaths of James Alderson, Terry Smith, Donnie Swindle and Amy Wright at a home in southeast Oklahoma City. The court handed him two death sentences for the killings of Wright and Alderson after evidence showed he chased the duo as they were trying to flee and then shot them from behind, KFOR reported.

During a clemency hearing in December, Gilbert did not deny his involvement in the shooting deaths. However, his attorney, Robert Nance, argued his client suffered from a learning disability. He was allegedly abandoned by his mother at a young age, and had begun abusing methamphetamine on a nearly daily basis beginning at age 12.

“He’s a different man than he was,” Nance told the Pardon and Parole Board at the time, the New York Post reported, citing the Associated Press. “I think he needs a certain amount of forgiveness because he grew up in an environment that was almost exclusively negative.”

Through a video link, Gilbert also testified he had been using meth for days before the killings, and remembered little about the crimes.

“I do understand that I’m guilty and I accept that,” he said at the time. “There’s nothing more that I know to say to you all than I am truly sorry for what I’ve done to all these families.”

Prosecutors said Gilbert, his brother David Postelle, father Brad Postelle and another man carried out the killings in a “blitz attack.” They were reportedly motivated by their belief that Swindle was responsible for a motorcycle accident that left Brad seriously injured. However, there was no evidence Swindle was involved in the crash.

Gilbert's brother was handed a life imprisonment sentence. In a trial held in 2006, their father was ruled incompetent, and Randal Byus, the fourth man involved in the murders, cooperated with the police and pleaded guilty. His charges were reduced in 2008.

Oklahoma, which at a time had one of the busiest death chambers in the country, put a hold on executions in 2015 after a botched lethal injection and drug mix-ups in 2014 led to an inmate being executed with the wrong drug.

lethal injection
The Texas death chamber is pictured in Huntsville, Texas, on June 23, 2000. Joe Raedle/Newsmakers