By David Beasley

ATLANTA (Reuters) - A decorated Vietnam War veteran convicted of murdering a Georgia sheriff's deputy in 1998 was put to death on Tuesday, state officials said, becoming the first death row inmate executed in the United States this year.

Andrew Brannan, 66, was executed by lethal injection at 8:33 p.m. EST at a prison in Jackson, Georgia, the state Attorney General's Office said in a statement.

The Georgia Supreme Court rejected a stay of execution on Tuesday afternoon, and the U.S. Supreme Court later denied two petitions to block his execution.

Brannan's lawyers did not dispute he shot Laurens County Sheriff's Deputy Kyle Dinkheller, 22, nine times during a traffic stop recorded by the deputy's patrol car video camera.

Kirk Dinkheller, the slain deputy's father, changed his Facebook profile picture on Tuesday to a photograph of his son's headstone.

"Nothing will ever bring my son back, but finally some justice for the one who took him from his children and his family," he wrote on the social media site earlier this month.

Brannan's attorneys sought to have his life spared, arguing the severe physical and mental toll from his service in Vietnam as an Army forward artillery observer was not fully explained to a jury.

Brannan had suffered from combat-related post-traumatic stress disorder and was prone to flashbacks of the war, his attorneys said.

Georgia's Board of Pardons and Paroles on Monday refused to commute Brannan's sentence to life in prison without parole.

His attorneys said in court papers filed with the high court that Brannan had no criminal record before killing the deputy.

"Mr. Brannan's case makes clear that it is time for this court to recognize a categorical exemption from execution for American combat veterans whose service to this country resulted in severe mental trauma" that contributed to their crime, the attorneys wrote in a failed petition.

Brannan's attorney Joe Loveland said in a phone interview that Brannan was told on Tuesday his case had drawn interest from veterans.

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Loveland said his client responded, "I am proud to have been able to walk point for my comrades, and pray that the same thing does not happen to any of them.”

Georgia's governor does not have the power to grant last-minute clemency to a death row inmate.

Brannan received Army commendations and a Bronze Star, one of the highest individual military awards, according to his lawyers.

(Additional reporting and writing by Alex Dobuzinskis in Los Angeles and Colleen Jenkins in Winston-Salem, North Carolina,; Editing by Jeffrey Benkoe, Peter Cooney and Eric Beech)