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An Ohio man convicted of back-to-back murders 25 years ago sang a hymn as he was executed Wednesday morning, media witnesses reported.

After Gary Otte apologized to relatives of his victims and sang the religious song "The Greatest Thing," he uttered his last words, a line attributed to Jesus Christ during his crucifixion: "Father, forgive them for they know not what they’re doing."

Gary Otte was put to death Wednesday. Ohio Department of Rehabilitation and Corrections via AP

Journalists who witnessed the execution did not report any apparent problems like the breathing troubles and prolonged deaths that have occurred during some other lethal injections. The Associated Press said Otte was pronounced dead at 10:54 a.m.

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He was the second inmate put to death since Ohio ended a three-year execution hiatus prompted by a lethal injection that raised questions about the drugs being used.

In a tweet on the eve of the execution, his attorney, Vickie Werneke, said that while Otte had fought vigorously to stop the state from killing him, he was "at peace." Prison officials said he did not sleep the night before the execution.

Otte, 45, was sent to death row for fatally shooting Robert Wasikowski and Sharon Kostura during home invasion robberies in a Cleveland suburb in 1992.

His last-ditch appeals included claims that use of the execution sedative midazolam is unconstitutional and that he should have been spared the death penalty because he was under 21 at the time of the crime.

The anti-execution activist Sister Helen Prejean also took up Otte's cause, tweeting that he has a low IQ and psychological problems.

But the U.S. Supreme Court and the state's highest court declined to halt the execution.

Ohio plans to execute Gary Otte tomorrow morning. Gary suffers with mental illness and addictions that date back to his childhood. Thread: — Sister Helen Prejean (@helenprejean) September 12, 2017

The state has scheduled another two dozen executions between now and 2020.