Jackson, Georgia (CNN) -- Troy Davis, whose case drew international attention, was put to death by lethal injection for the 1989 killing of an off-duty police officer in Savannah, Georgia, prison officials announced Wednesday night.





Until the very end, Davis maintained his innocence.





After he was strapped to the death gurney, he lifted his head to address the family of the slain officer.





He told the family of Mark MacPhail that he was not responsible for the officer's death and did not have a gun at the time, according to execution witnesses.





Davis said the case merited further investigation, talking fast as officials prepared to give him the lethal cocktail.





The execution followed the U.S. Supreme Court's rejection of a stay, allowing the state to proceed. Davis was declared dead at 11:08 p.m. ET.





Throughout the day, Davis' lawyers and high-profile supporters had asked the state and various courts to intervene, arguing he did not murder MacPhail in 1989.





Davis initially had been scheduled to die by lethal injection at 7 p.m. ET. But the proceeding was delayed more than three hours as the justices pondered a plea filed by his attorney.





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 who held a vigil outside the prison. Before the U.S. Supreme Court's decision, she said officials needed to take more time to examine the case.





"When you are looking at someone's life, you can't press rewind," she said.





More than 100 officers, many in riot gear, stood guard over the largely-quiet gathering, which featured candles, occasional prayers and songs.





"Tonight the state of Georgia legally lynched an innocent man," Davis' lawyer Thomas Ruffin Jr. said. "Tonight I witnessed something tragic."





Amnesty International condemned the execution in a statement.





"The U.S. justice system was shaken to its core as Georgia executed a person who may well be innocent. Killing a man under this enormous cloud of doubt is horrific and amounts to a catastrophic failure of the justice system," Amnesty said.





Anneliese MacPhail, the slain officer's mother, said she was relieved and that justice was served.





Davis' 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' supporters cheered and hugged each other when news of the earlier delay reached them.





Davis' attorneys started the day by asking a judge in Jackson, where Georgia's death row is located, to halt the proceeding, citing a new analysis they say shows ballistics testimony at his trial was "inaccurate and misleading."





They also note that a federal judge found in 2010 that a jailhouse informer's testimony that Davis confessed to killing MacPhail was "patently false" and that prosecutors knew a key eyewitness account was wrong.





"Clearly, the fact that Mr. Davis' death sentence rests in part on 'patently false' and egregiously inaccurate and misleading testimony, evidence and argument renders the death sentence fundamentally unfair, unreliable and therefore violative of the Eighth and Fourteenth Amendments," his attorneys argued in a motion filed Wednesday morning.





That appeal was denied Wednesday afternoon. The state Supreme Court followed suit a short time later, leading his attorneys to turn to the U.S. Supreme Court in the final hour before the execution.





Davis has been scheduled to die three times before, most recently in October 2008. That time, the U.S. Supreme Court halted the execution two hours before
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