Ernest Johnson was put to death on Tuesday for killing three workers during a convenience store robbery in Missouri nearly three decades ago, despite his intellectual capacity being under question.

The state of Missouri executed Johnson even as objections were raised by racial justice activists, lawmakers, and even the pope.

 Johnson died from an injection of pentobarbital at the state prison in Bonne Terre. He was pronounced dead at 6:11 pm. It was the first execution in Missouri since May 2020 and just the seventh in the US this year.

Johnson’s attorney had claimed that executing him would violate the 8th Amendment to the US Constitution, which prohibits executing intellectually disabled people.

Johnson had a history of scoring extremely low on IQ tests, dating back to childhood. His attorney, Jeremy Weis, said Johnson also was born with fetal alcohol syndrome and lost about one-fifth of his brain tissue when a benign tumor was removed in 2008.

A representative for Pope Francis was among those who urged Republican Governor Mike Parson to grant clemency, telling Parson in a letter that the pope “wishes to place before you the simple fact of Mr. Johnson’s humanity and the sacredness of all human life.” Parson announced on Monday that he would not intervene.

It wasn’t the first time a pope has sought to intervene in a Missouri execution. In 1999, during his visit to St. Louis, Pope John Paul II persuaded Democratic Gov. Mel Carnahan to grant clemency to Darrell Mease, weeks before Mease was to be put to death for a triple killing. Carnahan, who died in 2000, was a Baptist, as is Parson.

In 2018, Pope Francis changed church teaching to say capital punishment can never be sanctioned because it constitutes an “attack” on human dignity. Catholic leaders have been outspoken opponents of the death penalty in many states.

Racial justice activists and two Missouri members of congress — Democratic US Representatives Cori Bush of St. Louis and Emmanuel Cleaver of Kansas City —also called on Parson to show mercy to Johnson, who is Black.

But Parson announced Monday he would not grant clemency, and the courts declined to intervene.

Johnson had previously asked that his execution be carried out by firing squad. His lawyers argued that Missouri’s lethal injection drug, pentobarbital, could trigger seizures due to the loss of the brain tissue when the tumor was removed. Missouri law does not authorize execution in that manner.

Johnson’s crime shook the central Missouri city of Columbia nearly 28 years ago.

Johnson was a frequent customer of a Casey’s General Store. Court records show that on February 12, 1994, he borrowed a .25-caliber pistol from his girlfriend’s 18-year-old son, with plans to rob the store for money to buy drugs.

In a 2004 videotaped interview with a psychologist shown in court, Johnson said he was under the influence of cocaine as he waited for the last customer to leave at closing time. Three workers were in the store: manager Mary Bratcher, 46, and employees Mabel Scruggs, 57, and Fred Jones, 58.

On the video, Johnson said he became angry when Bratcher, who claimed not to have a safe key, tried to flush it down the toilet. He shot the victims with the borrowed gun, then attacked them with a claw hammer. Bratcher also was stabbed in the hand with a screwdriver. Police found two victims in the store’s bathroom, and the third in a cooler.

Johnson was sentenced to death in his first trial and two other times. The second death sentence, in 2003, came after the U.S. Supreme Court ruled that executing the mentally ill was unconstitutionally cruel. The Missouri Supreme Court tossed that second death sentence, and Johnson was sentenced a third time in 2006.

Of the six previous executions in the country this year, three were in Texas, and three involved federal prisoners.

(With inputs from AP)