MONTGOMERY, Ala. — Alan Eugene Miller became the second man in the nation executed by nitrogen gas Thursday when the state of Alabama put him to death for a 1999 triple homicide, after failing to do so by lethal injection in 2022.

Miller was taken into the execution chamber on Thursday evening at the Holman Correctional Facility in Atmore, and was pronounced dead at 6:38 p.m., Alabama Gov. Kay Ivey said in a statement. Miller gasped, shook, and struggled against his restraints for two minutes after the gas began to flow.

He continued to gasp and move for several more minutes after apparently losing consciousness, movements that Alabama Department of Corrections Commissioner John Hamm described as expected and "involuntary."

Miller, 59, was convicted of killing three people during a pair of 1999 workplace shootings in suburban Birmingham, Alabama. He was living in Autauga County at the time.

He had been on death row since 2000 and was set to be executed by lethal injection in September 2022, but staff could not gain access to his veins for the IV lines before his death warrant expired. Miller said that during the aborted 2022 lethal injection attempt, prison staff poked him with needles for over an hour as they tried to find a vein and at one point left him hanging vertically as he lay strapped to a gurney.

Miller and his defense team reached a deal with the state that lethal injection would not be used in a second execution attempt, choosing nitrogen gas hypoxia instead, court documents reveal.

Nitrogen hypoxia:Why Alabama's execution of Kenneth Smith stirs ethical controversy.

What happened during the execution

There was a clock in the death chamber at William C. Holman Correctional Facility but media witnesses were not allowed watches. The state called its new protocol "the most painless" execution method yet, and predicted that Smith would lose consciousness and suffocate within a few seconds of pure nitrogen flowing through an industrial-safety respirator mask strapped to his face.

That did not happen. Multiple witnesses, including five journalists and members of Smith's family, saw Smith heaving against his restraints and convulsing as the nitrogen flowed, and it appeared to take him several minutes to lose consciousness.

The method has drawn national and international scorn and media attention, including a protest from the Vatican, due to its untested history and perceived physical effects on the condemned. Nitrogen hypoxia had only been used as an execution method in the U.S. once when Alabama executed Kenneth Eugene Smith in January.

The Biden administration has said it was "deeply troubled" by the new method, which has been condemned by senior U.N. human rights officials who say it may amount to torture or cruel treatment.

Commissioner: 'Agonal breathing' was expected

In a news conference immediately after the execution, Hamm described Miller’s reaction as “involuntary body movements.” He said the movements and the “agonal breathing” were expected and that the nitrogen gas flowed for about 15 minutes. Hamm described the execution as going according to department protocol.

“Just as Alan Miller cowardly fled after he maliciously committed three calculated murders in 1999, he has attempted to escape justice for two decades," Alabama Gov. Kay Ivey said. "Tonight, justice was finally served for these three victims through the execution method elected by the inmate. His acts were not that of insanity, but pure evil. Three families were forever changed by his heinous crimes, and I pray that they can find comfort all these years later.”

Alabama has offered to help others adopt nitrogen-asphyxiation executions, saying they are a simpler alternative for states struggling to find lethal-injection drugs.

Advocacy groups against capital punishment have long pressured pharmaceutical companies to forbid their drugs be used in executions, and have turned their attention to nitrogen suppliers and mask makers, including the maker of the Allegro Safety mask Alabama acquired for its executions.

Stephanie Boucher, a spokesperson for Allegro's parent company Walter Surface Technologies in Connecticut, said the company will not comment on the use of its masks in executions.

1999 murders

Miller, a delivery truck driver, was convicted in the fatal 1999 workplace shootings of Lee Holdbrooks, Scott Yancy, and Terry Jarvis. Prosecutors said Miller killed Holdbrooks and Yancy at one business and then drove to another location to shoot Jarvis. Each man was shot multiple times.

Testimony indicated Miller was delusional and believed the men were spreading rumors about him. Jurors convicted Miller after 20 minutes of deliberation and then recommended a death sentence, which a judge imposed.

Alabama has plans to conduct at least two more executions this year. Derrick Ryan Dearman is scheduled to die by lethal injection on Oct. 17, and Carey Dale Grayson is scheduled to die by nitrogen hypoxia on Nov. 21.

Contact Montgomery Advertiser reporter Marty Roney at [email protected].

Contributing: Reuters