James Pavatt, 73, was executed by lethal injection at the state penitentiary in McAlester. He was pronounced dead at 10:12 a.m. CST, Oklahoma Department of Corrections spokesperson Lance West said.
In Texas, John Allen Rubio was set to be put to death later Thursday. The 46-year-old was convicted of beheading three young children he was raising in a 2003 killing that rattled a community along the U.S.-Mexico border.
The U.S. is on track to surpass 40 executions for a second consecutive year, a pace driven by Florida as the death penalty comes under renewed attention. Last week, California Gov. Gavin Newsom announced he would commute hundreds of death sentences before leaving office, which experts say would be the largest mass clemency in American history.
Pavatt was convicted of first-degree murder and conspiracy to commit murder in the death of Rob Andrew, a 39-year-old advertising executive. He was fatally shot in the garage of the Oklahoma City home he'd previously shared with his wife as he picked up their two young children before Thanksgiving.
Pavatt, who attended the same church as the Andrew family, had been having an affair with Rob Andrew's wife, Brenda Andrew. She was convicted at a separate trial and sentenced to death.
Weeks before the shooting, Rob Andrew told police someone was trying to kill him after the brake lines on his car were cut. Brenda Andrew told police after her husband was killed that masked intruders shot her in the arm and fatally shot him.
Pavatt and Brenda Andrew went to Mexico with her two children after the shooting and were arrested three months later while reentering the U.S.
At a clemency hearing last month, Pavatt said he was "not guilty of shooting anyone," and that he'd fallen in love with Brenda Andrew and believed "everything she told me."
"It was not until my trial that I began to see the extent to which I had been manipulated by Brenda," Pavatt told the board. "I can see why the jury believed that we were both involved in Rob's murder."
Prosecutors have said that Pavatt and Brenda Andrew plotted to kill her husband, and that no matter who fired the shots, both were equally guilty.
Rubio and his girlfriend, Angela Camacho, were accused in the killings of 3-year-old Julissa Quesada, 14-month-old John E. Rubio and 2-month-old Mary Jane Rubio in the squalid, windowless apartment they shared in Brownsville, located on Texas' border with Mexico.
Camacho pleaded guilty and is serving a life sentence.
Rubio's first capital murder conviction in the killings was overturned by an appeals court, which ruled that statements by Camacho were wrongly allowed as evidence in his trial. Rubio again pleaded not guilty by reason of insanity for his second trial but he was once again convicted and sentenced to death.
Rubio, according to court records, wasn't the biological father of the two older children but treated them as if they were his own.
At various points, Rubio claimed the children were possessed and that he was the "chosen one" intended to save the world. Defense experts diagnosed Rubio as suffering from paranoid schizophrenia, a determination rejected by prosecution experts.
Defense experts testified his childhood — filled with violence at home, "toxic" parents, drug use and prostitution — damaged him developmentally.
The apartment building where the children were killed was later demolished and the land was turned into a park and a community garden.
Rubio is set to be executed at the state prison in Huntsville.