McAlester, Oklahoma - A 59-year-old man was executed in the state of Oklahoma on Thursday for a double murder that he claimed was committed in self-defense.

Phillip Hancock was put to death by three-drug lethal injection at the Oklahoma State Penitentiary in McAlester, a spokesperson for the Oklahoma Department of Corrections said.

The Oklahoma Pardon and Parole Board had previously recommended that Hancock be granted clemency, but these recommendations were ultimately denied by Governor Kevin Stitt.

The governor's decision to deny a stay of execution was reportedly delayed until after the execution's originally scheduled start time of 10 AM.

Crime Grizzly details emerge about bodies likely belonging to missing Australian and US surfers

Once word came through from Stitt, the execution commenced after 11 AM.

"I can’t imagine the anxiety that Phillip Hancock must have felt as Governor Stitt again waited until beyond the last minute to reject clemency," Reverend Don Heath, chair of the Oklahoma Coalition to Abolish the Death Penalty, said in a statement.

Hancock was sentenced to death for the April 2001 murders of Robert Jett and James Lynch, members of a biker gang. He said that he shot Jett and Lynch during a struggle after they tried to force him into a cage at Jett's Oklahoma City residence.

Even members of the governor's own Republican party condemned the execution, including State Representative Kevin McDugle, who called it "simply not justice."

McDugle said in a statement that he had learned of "serious problems in Oklahoma's death penalty system" while following the case.

He called for a halt to any further executions in the state "until we can ensure that only people who truly deserve capital punishment are sentenced to death."

There have been 24 executions in the United States this year. No further executions are scheduled for the remainder of the year.

According to a recent Gallup Poll, 53% of Americans support the death penalty for someone convicted of murder, the lowest level since 1972.

Capital punishment has been abolished in 23 US states, while three others – California, Oregon, and Pennsylvania – have observed a moratorium on its use.

Executions have been carried out in five states this year: Alabama, Florida, Missouri, Oklahoma, and Texas.

The death penalty has been primarily carried out by lethal injection in recent years, but Alabama intends to execute a person next year using nitrogen gas.

Alabama Governor Kay Ivey has set January 25 as the execution date for Kenneth Smith (58) who was sentenced to death for a 1988 murder.