TRIGGER WARNING | Alabama execution: Witness says Smith struggled like 'fish out of water'

Trigger warning: Some readers may find details of this report disturbing. Discretion is advised.

A witness who saw the nitrogen gas execution of 58-year-old Kenneth Eugene Smith, while speaking to the Daily Mail, spoke about how the Alabama inmate wriggled in pain when he was suffocated to death.

Smith was taken to the execution chamber located at the William C. Holman prison in Atmore and was given a tight mask to wear on his face.

Speaking about the moment when the convict was executed, spiritual guide Jeff Hood said that it was the “worst thing” he had ever witnessed in his life.

He added that even prison officials were left horrified seeing Smith withering in pain for almost 22 minutes before dying. “When they turned the nitrogen on, he began to convulse, he popped up on the gurney over and over again, he shook the whole gurney,” said Hood.

"I mean, it really was like watching someone put a plastic bag over someone's head and just to see what happens, and holding it as tight as they can, as long as they can, to watch the person resist and shake," saidHood, while speaking toNBC News.

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"They repeatedly said that he would not be able to resist the nitrogen, and would be unconscious within seconds. And then he looks like a fish out of water," he said

At one given point, the convict struggled against his restraints as his wife Deanna shed tears seeing his condition from the witness box.

The man spoke his last words through the gas mask after he made a heart sign using his left hand for his family members. “Tonight Alabama causes humanity to take a step backwards... I’m leaving with love, peace and light,” Smith said, as reported by the Daily Mail.

‘Unbelievable evil was unleashed': Smith's pastor John Ewell

Meanwhile, Smith's pastor John Ewell said that the convicted killer was “really struggling” with the thoughts of how he would be executed. As per the officials, the man hardly ate anything from his final meal, which was hash browns, T-bone steak, eggs and A1 Sauce from Waffle House.

Hood added that the contraption which was used for executing Smith appeared like a firefighter mask.

“I could see the corrections officers, I think they were very surprised that this didn't go smoothly - one of the state officials in the room was so nervous she was tap dancing,” he added while speaking to the Daily Mail.

Watch:Alabama to carry out first Nitrogen gas execution

“(Smith) kept breathing for what could possibly be up to nine minutes, ten minutes, unbelievable evil was unleashed tonight in Alabama,” he said, adding that since he had witnessed five executions previously, he thinks that “lethal injection is preferable every single day.”

Meanwhile, Alabama officials have called the nitrogen hypoxia method an “effective and humane method of execution.”

The court had given a death sentence to Kenneth Eugene Smith in 1996 for a 1988 murder and he was pronounced dead at 8:25 pm (0225 GMT Friday), as per local media, which cited southern state Governor Kay Ivey's statement.

(With inputs from agencies)