A Missouri man who shot and killed two jailers nearly 23 years ago during a failed bid to help an acquaintance escape from a rural jail was executed Tuesday evening.

Michael Tisius, 42, received a lethal injection of pentobarbital at the state prison in Bonne Terre and was pronounced dead at 6:10 p.m., authorities said. He was convicted of the June 22, 2000, killings of Leon Egley and Jason Acton at the small Randolph County Jail.

Tisius breathed hard a few times as the drug was administered, then fell silent. His spiritual adviser, Melissa Potts-Bowers, was in the room with him. Because the execution chamber is surrounded by soundproof glass, it's not known what they were saying to each other.

In a final written statement, Tisius said he tried hard "to become a better man," and he expressed remorse for his crimes.

"I am sorry," he wrote. "And not because I am at the end. But because I truly am sorry."

Tisius' lawyers had urged the U.S. Supreme Court to block the execution, alleging in appeals that a juror at a sentencing hearing was illiterate, in violation of Missouri law. The court rejected that motion Tuesday afternoon.

The New York Times reports that some of the jurors who decided Tisius should get the death penalty had said prior to his execution they would have backed or wouldn't have objected if Missouri Gov. Mike Parson commuted the sentence to life in prison.

But Parson, a Republican, refused to on Monday, saying in a statement, "It's despicable that two dedicated public servants were murdered in a failed attempt to help another criminal evade the law. The state of Missouri will carry out Mr. Tisius's sentences according to the Court's order and deliver justice."

Advocates cite Michael Tisius' childhood in appeals

The Supreme Court has already turned aside another argument — that Tisius should be spared because he was just 19 at the time of the killings. A 2005 Supreme Court ruling bars executions of those under 18 when their crime occurred, but attorneys for Tisius argued that even at 19 when the killings occurred, Tisius should have his sentence commuted to life in prison without parole.

Advocates for Tisius also have said he was largely neglected as a child and was homeless by his early teens. In 1999, as an 18-year-old, he was jailed on a misdemeanor charge for pawning a rented stereo system.

In June 2000, Tisius was housed on a misdemeanor charge at the same county jail in Huntsville with inmate Roy Vance. Tisius was about to be released, and court records show the men discussed a plan in which Tisius, once he was out, would help Vance escape.

Just after midnight on June 22, 2000, Tisius went to the jail accompanied by Vance's girlfriend, Tracie Bulington. They told Egley and Acton that they were there to deliver cigarettes to Vance. The jailers didn't know that Tisius had a pistol.

At trial, Bulington testified that she looked up and saw Tisius with the gun drawn, then watched as he shot and killed Acton. When Egley approached, Tisius shot him, too. Both officers were unarmed.

Tisius found keys at the dispatch area and tried to open Vance's cell, but couldn't. When Egley grabbed Bulington's leg, Tisius shot him several more times.

Tisius and Bulington fled but their car broke down later that day in Kansas. They were arrested in Wathena, Kansas, about 130 miles west of Huntsville. Tisius confessed to the crimes.

Bulington and Vance are serving life sentences on murder convictions.

Defense attorneys have argued that the killings were not premeditated. Tisius, they said, intended to order the jailers into a holding cell and free Vance and other inmates. Tisius' defense team issued a video last week in which Vance said he planned the escape attempt and manipulated Tisius into participating.

2 Missouri executions so far this year

The execution was the 12th in the U.S. this year and third in Missouri. Only Texas, with four, has executed more people than Missouri this year.

Amber McLaughlin, 49, who killed a woman and dumped the body near the Mississippi River in St. Louis, was put to death in January. The execution was believed to be the first of a transgender woman in the U.S. Raheem Taylor, 58, was executed in February for killing his live-in girlfriend and her three children in 2004 in St. Louis County.

Another Missouri execution is scheduled for Aug. 1. Johnny Johnson was convicted of sexually assaulting and killing a 6-year-old girl in St. Louis County in 2002.

In:
• Death Penalty
• Capital Punishment
• Executions