Carman Deck, 56, was put to death by lethal injection at 6:10 p.m. at the state prison. He is the fifth death row inmate to be executed in the U.S. this year.
Deck was convicted of killing James and Zelma Long, both in their 60s, after he stopped at their country home in De Soto in July 1996, ostensibly to ask for directions but with the intention to rob them.
He knew the Longs’ grandson and the fact that they kept a safe in their home. After the couple invited him and his sister into the home, he held them at gunpoint and made Zelma Long open the safe and give him the contents.
He then told them to lie face down on their bed and stood there for 10 minutes before deciding to shoot them both twice in the head.
The U.S. Supreme Court and Republican Gov. Mike Parson both declined to halt the execution.
The Longs "were innocent victims of Carman Deck’s heinous violence. Tonight, justice was served," Parson said in a statement.
Deck spoke inaudibly as the lethal concoction was injected.
In a written statement, Deck said, "My hope is that one day the world will find peace and that we all will learn to be kind and loving to one another. We all are a part of this journey through life, connected in every way. Please give love, show love, BE LOVE!"
He confessed to the crime after being arrested outside his sister's apartment the same night as the killings and a decorative canister from the Long home was found in his car, prosecutors said. He was sentenced to death in 1998.
The Missouri Supreme Court later overturned the sentence because of errors made by his lawyer and the U.S. Supreme Court overturned his second sentence in 2005, ruling that the sentencing jury was prejudiced by him being shackled in the courtroom.
He was sentenced to death for the third time in 2008. Nine years later, U.S. District Judge Catherine Perry determined that "substantial" evidence arguing against the death penalty in Deck’s first two penalty phases was unavailable for the third because witnesses had died, couldn’t be found or declined to cooperate.
His sentence was restored in 2020 by a three-judge panel of the 8th U.S. Circuit Court of Appeals.
His attorney, Elizabeth Unger Carlyle, argued for clemency based on childhood neglect as well as physical and sexual abuse she claimed he suffered.
Carlyle also said Deck was raped at age 19 while in prison for a robbery offense and was transformed from a "non-violent" thief into a person who "committed two terrible murders."
The Associated Press contributed to this report.