JARRATT, Va. » A 49-year-old convicted of murdering three people in Virginia and California nearly three decades ago was executed on Thursday after a series of last-minute appeals failed.

Alfredo Prieto was pronounced dead at 9:17 p.m. at the Greensville Correctional Center in Jarratt. Prieto was injected with a lethal three-drug combination, including the sedative pentobarbital, which Virginia received from the Texas prison system.

Prieto, wearing glasses, jeans and a light blue shirt, did not resist and showed no emotion as he was strapped to the gurney.

“I would like to say thanks to all my lawyers, all my supporters and all my family members,” he said, before mumbling, “Get this over with.”

The El Salvador native was sentenced to death in Virginia in 2010 for the murder of a young couple more than two decades earlier. Rachael Raver and her boyfriend, Warren Fulton III, both 22, were found shot to death in a wooded area a few days after being seen at a Washington, D.C., nightspot.

Prieto was on death row in California at the time for raping and murdering a 15-year-old girl and was linked to the Virginia slayings through DNA evidence. California officials agreed to send him to Virginia on the rationale that it was more likely to carry out the execution.

He has been connected to as many as six other killings in California and Virginia, authorities have said, but he was never prosecuted because he had already been sentenced to death.

Prieto is the first inmate to be executed in in Virginia in nearly three years.

Virginia’s lethal injection protocol calls for the use of pentobarbital, a sedative, at the beginning of the execution. That’s followed by rocuronium bromide, which halts an inmate’s breathing, and potassium chloride, which stops the heart.

Prieto looked calm as he entered the execution chamber at 8:53 p.m. The warden stepped behind the curtain at 9:09 p.m. and shortly afterward officials began administering the drugs. Prieto’s chest rose and fell several times but he made no sounds. He was motionless after a few minutes.

Prieto’s attorneys filed a lawsuit Wednesday seeking to halt the execution until Virginia officials disclose more information about the supply of pentobarbital, which Virginia received from Texas because another sedative it planned to use expired. They said they were concerned about the quality of the drugs and they fear that they will cause a cruel and painful death.

But U.S. District Court Judge Henry E. Hudson lifted a temporary order blocking Prieto’s execution on Thursday, saying that Prieto’s lawyers had not adequately shown that the drugs are unsafe. He said unwarranted delay of the execution would be harmful for those victimized by Prieto’s crimes, a harm “magnified here by the appalling number of people that Prieto has killed, raped, or otherwise injured.”

“It is time for this to end,” said Margaret O’Shea, a lawyer from Attorney General Mark Herring’s office, who urged the judge to dismiss Prieto’s appeal on Thursday. “It is time for the carousel to end.”

Prieto had also asked the U.S. Supreme Court to intervene, saying he’s intellectually disabled, and therefore ineligible for the death penalty. But the high court declined to grant his requests to stay the execution on Thursday.

His attorneys argued that the state should reconsider whether Prieto is intellectually disabled because the measure used during his 2008 trial was unconstitutional. The Supreme Court ruled last year that Florida can’t use rigid cutoffs on IQ test scores to determine whether someone is intellectually disabled. Virginia had a nearly identical law.

“The Commonwealth had the opportunity to correct that error, and chose not to,” Attorney Rob Lee said in a statement after the execution. “Our nation prohibits the execution of persons with intellectual disability; in this case, the state was unwilling to ensure that protection was honored before carrying out its harshest penalty.”

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Associated Press writer Alan Suderman in Richmond, Virginia, contributed to this report.