An Alabama inmate convicted in the 1994 killing of a female hitchhiker cursed at the prison warden and made obscene gestures with his hands shortly before he was put to death Thursday evening in the nation’s third execution using nitrogen gas.

Carey Dale Grayson, 50, was executed at the William C. Holman Correctional Facility in southern Alabama. He was one of four teens at the time convicted of killing Vickie Deblieux, 37, as she was hitchhiking through Alabama on the way to her mother’s home in Louisiana. The woman was attacked, beaten and thrown off a cliff.

ALABAMA DEATH ROW INMATE EXECUTED WITH NITROGEN GAS, NATION’S FIRST BY A NEW METHOD IN 42 YEARS

Strapped to a gurney with a blue-rimmed gas mask strapped to his face, Grayson raised both of his middle fingers and cursed at the prison warden. When the prison warden asked for his final statement, Grayson responded with an obscenity. The warden turned off the microphone. Grayson appeared to address the witness room with state officials.

Abe Bonowitz of Death Penalty Action leads a protest outside the Capitol in Montgomery, Ala., on Monday, against a scheduled execution in Alabama using nitrogen gas.  (Kim Chandler/Associated Press)

It was unclear when the gas began flowing. Grayson shook and pulled against the gurney restraints. His sheet-wrapped legs at one point lifted off the gurney in the air. He then clenched his fist and appeared to struggle to try to gesture again, then took a series of gasping breaths for several minutes before becoming still.

Grayson was pronounced dead at 6:33 p.m.

Alabama began using nitrogen gas earlier this year to carry out some executions. The method involves placing a respirator gas mask over the person’s face to replace breathable air with pure nitrogen gas, causing death by lack of oxygen.

The execution was carried out hours after the U.S. Supreme Court turned down Grayson’s request for a stay. His attorneys had argued that the method needed more scrutiny before being used again.

Deblieux’s mutilated body was found at the bottom of a bluff near Odenville, Alabama, on Feb. 26, 1994. She was hitchhiking from Chattanooga, Tennessee, to her mother’s home in West Monroe, Louisiana, when the four teens offered her a ride. Prosecutors said the teens took her to a wooded area and attacked and beat her. They threw her off a cliff and later returned to mutilate her body.

A medical examiner testified that Deblieux’s face was so fractured that she was identified by an earlier X-ray of her spine. Investigators said the teens were identified as suspects after one of them showed a friend one of Deblieux’s severed fingers and boasted about the killing.

Gov. Kay Ivey issued a statement minutes after Thursday’s execution saying she was praying for the murder victim’s loved ones to find closure and healing still decades after the crime.

Carey Dale Grayson (Alabama Department of Corrections via AP)

“Some thirty years ago, Vicki DeBlieux’s journey to her mother’s house and ultimately, her life, were horrifically cut short because of Carey Grayson and three other men. She sensed something was wrong, attempted to escape, but instead, was brutally tortured and murdered,” Ivey said in the statement.

Grayson’s crimes “were heinous, unimaginable, without an ounce of regard for human life and just unexplainably mean. An execution by nitrogen hypoxia (bears) no comparison to the death and dismemberment Ms. DeBlieux experienced,” she added.

Grayson was the only one of the four teens who faced a death sentence since the other teens were under 18 at the time of the killing. Grayson was 19. Two of the teens were initially sentenced to death but those sentences were set aside when the Supreme Court banned the execution of offenders who were younger than 18 at the time of their crimes. Another teen involved in Deblieux’s killing was sentenced to life in prison.

Grayson’s final appeals had focused on a call for more scrutiny of the nitrogen gas method. His lawyers argued that the person experiences “conscious suffocation” and that the first two nitrogen executions did not result in swift unconsciousness and death as the state had promised. Lawyers for the Alabama attorney general’s office asked the justices to let the execution proceed, saying a lower court found Grayson’s claims speculative.

Alabama maintains the method is constitutional. But critics — citing how the first two people executed shook for several minutes — say the method needs more scrutiny, particularly if other states follow Alabama’s path.

“The normalization of gas suffocation as an execution method is deeply troubling,” said Abraham Bonowitz, executive director of Death Penalty Action, a group seeking to abolish the death penalty.

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No state other than Alabama has used nitrogen hypoxia to carry out a death sentence. In 2018, Alabama became the third state — along with Oklahoma and Mississippi — to authorize the use of nitrogen gas to execute prisoners.

Some states are looking for new ways to execute inmates because the drugs used in lethal injections, the most common execution method in the United States, are increasingly difficult to find.