Ernest Johnson was executed in Missouri on Tuesday, despite claims by his attorney and death penalty opponents that he had an intellectual disability and that killing him violated the Constitution.

Johnson, 61, was executed by lethal injection at a state prison in Bonne Terre after being convicted in the murders of three convenience store employees nearly three decades ago. He was pronounced dead at 6:11 p.m. local time, according to a state corrections spokeswoman.

Among those who spoke out against the execution were Pope Francis, two members of Congress, and former Democratic governor Bob Holden. On Monday, Republican Gov. Mike Parson denied Johnson’s request for clemency and stated that the state would carry out the execution. On Tuesday, the United States Supreme Court denied an application for a stay of execution.

In a filing to the Supreme Court on Tuesday, Johnson’s legal team stated that IQ tests showed he had the intellectual capacity of a child and that there would be “no tangible harm” if his execution was postponed while questions about whether lower courts “constitutionally considered” his disability were investigated further.

“This Court has said states simply cannot execute the intellectually disabled,” Johnson’s attorneys wrote, referring to a Supreme Court decision from 2002. Johnson’s execution was the first by Missouri prison officials since May 2020, when the pandemic halted state executions before Texas resumed them this year.

According to the spokeswoman, four relatives of the three people killed by Johnson in 1994 were present. According to a media witness, Johnson’s breathing became labored, but there were no visible signs of distress.

Democratic U.S. Reps. Cori Bush and Emanuel Cleaver were among Johnson’s supporters, urging Parson to reconsider his position. Bush, a racial justice activist, has also noted the racial disparities in the prison system and the death penalty for Black and Latino men, and believes that executing Johnson, who is Black, does not address the systemic issues.

According to a letter from Archbishop Christophe Pierre, the Vatican’s ambassador to the United States, last week, Francis expressed his support for Johnson and urged Parson to grant the inmate “some appropriate form of clemency.”

According to the letter, Francis declined to comment on the “circumstances of the crime,” instead emphasizing a larger moral choice that must be considered. “His Holiness wishes to bring to your attention the simple fact of Mr. Johnson’s humanity and the sanctity of all human life,” Pierre wrote.

Parson stated this week that Johnson was competent to be executed, noting that several courts, including Missouri’s highest court, had rejected his appeals over the years.

“The state is ready to deliver justice and carry out Mr. Johnson’s lawful sentence in accordance with the Missouri Supreme Court’s order,” he said in a statement.

Johnson had also requested a firing squad execution, which the Missouri Supreme Court denied in August. Last May, a majority of the United States Supreme Court declined to hear Johnson’s case, arguing that his brain damage puts him at risk of severe and painful seizures if he is executed by lethal injection.

According to attorney Jeremy Weis, Johnson was born with fetal alcohol syndrome and also lost one-fifth of his brain tissue when a benign tumor was removed in 2008. He added that the brain defect, which left a small hole in his skull, scar tissue, and a blank space where the tumor was removed, could cause him further pain. Missouri Attorney General Eric Schmitt, a Republican, responded Monday to Johnson’s request for a stay of execution, saying that what he was convicted of in 1994 belies his claims of intellectual disability.

Prosecutors claim Johnson fatally bludgeoned a manager, Mary Bratcher, 46, and employees Mabel Scruggs, 57, and Fred Jones, 58, during a closing-time robbery at the Casey’s General Store in Columbia on Feb. 12, 1994, with a claw hammer. According to court documents, he was stealing money to buy drugs.

Some of the victims’ family members advocated for his execution for his actions. Bob Holden, Missouri’s governor from 2001 to 2005, wrote in The Kansas City Star on Sunday that while his office oversaw 20 executions, Johnson’s case is an outlier due to questions about his mental capacity.