Robert Pruett was executed by Lethal Injection on Thursday for killing a prison guard in 1999. Pruett, 38, was pronounced dead at 6:46 PM in the execution chamber of the Texas State Penitentiary at Huntsville. The United States Supreme Court declined to stop the execution, though Pruett insisted that he was innocent.

Before he was injected with the lethal drug cocktail, Pruett made a final statement, acknowledging that he hurt a lot of people and he was sorry, the Houston Chronical reported. He also said that he was hurt by many people but didn’t hold any grudges.

He stated that he learned lessons in life “the hard way.”

Killer’s final words were ‘I’m done, warden’

Pruett’s friends were among the execution witnesses. As they watched through a window to the death chamber, he expressed his love for them. After he concluded speaking to his friends for the last time, he stated that he was ready to “go,” according to the Chronicle. “Nighty night” and “I’m done warden” were his final drug-free words. Pruett chanted, “Love. Light. It’s forever,” while a lethal dose of the sedative pentobarbital was injected.

He also shouted obscenities before dying, according to the Texas Tribune and additional media reports. He died 29 minutes after the pentobarbital was administered.

Pruett was the sixth condemned inmate executed by the Texas Department of Criminal Justice in 2017, U.S. News & World Report noted. Following the U.S. Supreme Court’s 1976 reinstatement of the death penalty, Pruett is among 544 inmates that have since been executed in the United States. Texas has exacted capital punishment more than any other state.

Nation’s highest court, parole board, and Texas governor declined inmate a reprieve from death

Pruett was within hours of being executed when the nation’s highest court turned down his appeal that could have spared his life. He was also denied clemency on Wednesday by the Texas Board of Pardons and Paroles, a panel that is comprised of six members, KCEN relayed.

Pruett’s attorneys asked Texas Governor Greg Abbott to grant a 120-day reprieve, which inevitably did not result.

Death penalty followed murder of maximum security prison corrections officer

The condemned inmate received the death penalty in 2002 after he murdered thirty-seven-year-old Daniel Nagle, according to several news organizations. Nagle was a corrections officer at William G. McConnell Unit, which is a maximum security prison in Beeville, TX.

Nagle’s body was discovered in a pool of blood. Next to the slain prison guard was a ripped up disciplinary report the officer wrote about Pruett. The inmate reportedly tried to violate prison rules when he wanted to take a sandwich into the facility’s recreation yard.

The stabbing evolved from Pruett’s dispute with Nagle, the Houston Chronicle noted.

Guard stabbed suffered fatal heart attack

An autopsy and prosecutors stated that Nagle suffered a fatal heart attack in the prison after Pruett stabbed him with a metal rod, KCEN wrote. Pruett, who was 20-years-old when Nagle was attacked and died, had already served several years of a 99-year sentence after he was convicted of acting as an accomplice to a murder that his father committed when he was 15.

Prosecutors asserted that Nagle was killed as a result of the disciplinary report against Pruett, who was steadfast in maintaining his innocence. The convicted killer recently claimed that “corrupt guards and inmates” framed him for a grievance report, according to the Tribune.

Prison guard’s widow witnessed and left execution saying, ‘Now it’s up to God’

Nagle’s relatives witnessed Pruett’s execution, according to the Chronicle. Approximately 100 corrections officers were standing in formation outside Huntsville Unit while capital punishment against Pruett was imposed.

The officers remained in formation until Nagle’s family members left the prison. Nagle’s widow, Cyrstal, stated, “Now it's up to God because Jesus is the one who does the final judgment.”