The US state of Texas has executed the 400th person since the state resumed capital punishment in 1982.
Johnny Ray Conner (32), who was convicted of shooting dead of a shop owner in Houston in 1998, was the 21st man put to death by lethal injection in Texas this year. He spent nearly eight years on death row.
Texas resumed the practice after the Supreme Court lifted a moratorium on it in 1976. Since then, 1,092 people have been executed in the United States, including Conner, according to statistics from the Death Penalty Information Center.
"It's a pretty sad day for the progression - or lack thereof - for human rights in this state," said Rick Halperin, president of the non-profit Texas Coalition To Abolish the Death Penalty. He called the state-ordered executions "barbaric and outdated."
The European Union urged the governor of Texas to halt all executions before the state carried out Conner's death sentence.
A spokesman for Texas Governor Rick Perry responded in a statement: "Texans long ago decided that the death penalty is a just and appropriate punishment for the most horrible crimes committed against our citizens."