The U.S. Supreme Court late Wednesday rejected a last-ditch appeal from Georgia death row inmate Troy Davis, allowing the state to proceed with the scheduled execution of the convicted killer.

The justices, in a brief order, turned aside a request for a stay of execution.

Davis’ lawyers and high-profile supporters had asked the state and various courts to intervene, arguing he did not murder an off-duty Savannah police officer.

Davis had been scheduled to die by lethal injection at 7 p.m. ET for the 1989 killing of Mark MacPhail. But the proceeding was delayed more than three hours as the justices pondered a plea filed by his attorneys after last-ditch appeals failed throughout the day.

Several hundred people, most of them opposing the proceeding, gathered outside the state prison in Jackson where Davis, 42, awaited his fate. Others held a vigil in a nearby church.

The inmate’s sister, Martina Davis-Correia, was among those waiting outside the prison. She said officials need to take more time to examine the case. “When you are looking at someone’s life, you can’t press rewind.”

At 10:30 p.m., more than 100 officers, many in riot gear, stood guard over the largely quiet gathering, which featured candles, occasional prayers and songs. At least three people who crossed the street had been taken away in handcuffs.

Davis’s supporters, who also rallied outside the U.S. Supreme Court building, argued that his conviction was based on the testimony of numerous witnesses who had recanted, including a jailhouse informer who claimed Davis had confessed.

“There’s a genuine feeling among people here and across the nation that we’re about to do the unthinkable,” said Isaac Newton Farris Jr., president of the Southern Christian Leadership Conference.

But prosecutors have stood by the conviction, and every appeal — including the last-minute petitions filed Wednesday — has failed.

Davis’s supporters cheered and hugged each other when news of the earlier delay reached them. But it did not sit well with McPhail’s mother, who remained at home.

“This delay again is very upsetting and I think really unfair to us, because we want this situation closed,” the slain officer’s mother, Anneliese MacPhail, told CNN’s “Anderson Cooper 360.” She said the execution would bring her “relief and maybe some peace.”

CNN’s David Mattingly, Vivian Kuo, Bill Mears, Gustavo Valdes and John Murgatroyd contributed to this report.