Arkansas has executed Ledell Lee in the US state's first use of the death penalty in 12 years.
It came after the US Supreme Court rejected a challenge arguing Arkansas was unfairly rushing several executions before its supply of a lethal injection drug expires at the end of April.
On Thursday the state's Supreme Court overturned a ruling blocking the use of a different drug.
Lee was convicted of murder and recently told the BBC he was innocent.
Arkansas plans to carry out two more executions on Monday, and one next Thursday.
He was pronounced dead at 23:56 local time on Thursday (04:56 GMT on Friday) at the state's death chamber in its Cummins Unit prison, a Department of Corrections spokesman said. His death warrant was due to expire at midnight.
Lee did not make a final statement. Instead of a last meal, he asked to receive communion, an official said, adding that he was given grape juice or water rather than sacramental wine.
Lee did not appear to suffer as the drugs took effect, according to a reporter selected to serve as a media witness.
Analysis: Aleem Maqbool, BBC News
It could barely have been a more tortuous few days for the family of Ledell Lee.
As well as speaking to him by phone, I met his mother Stella last week; a strong woman, mistrustful of officials (and of reporters), who insisted she knew her son to be innocent with every bone in her body.
Since then, she had hopes raised when it looked like a pharmaceutical company would win its battle to stop its drug being used to kill; or when a court ruled there was too much risk of extreme suffering for the lethal injection drug to be used; or when human rights groups filed petitions arguing Ledell had not had a fair murder trial as some observers have noted for years.
The legal battles were still going on even hours after her son had declined his 'last meal' and instead received communion.
At almost the last possible moment, the final legal obstacle was brushed aside and Ledell Lee was put to death.
One victim's relative, in the case of another prisoner due to be executed this month, said the prisoners' families had the luxury of being able to say a proper goodbye in a way that he never did.
But it has been hard to imagine what a mother must feel knowing her son is set to die at a certain time on a certain date.
He had been on death row for more than 20 years after he was convicted of beating Debra Reese to death with a tyre thumper in 1993.
He was arrested less than an hour after the killing when he had spent some of the money he had stolen from his victim.
Her family "had waited 24 years to see justice done", Arkansas Attorney General Deborah Rutledge said in a statement.
"I pray this lawful execution helps bring closure for the Reese family," she said.
Lee told the BBC's Aleem Maqbool in a recent interview that he was innocent, and death row was like a "living nightmare".
Crowds that had gathered to protest outside the Arkansas governor's mansion in Little Rock chanted and and held hands until Lee was pronounced dead just before midnight, and only four minutes before his death warrant had been due to expire.
The state had initially planned to carry out eight executions in 11 days, before the 30 April expiration date of its supply of the drug, midazolam - used together in lethal injections with two other drugs.
The first three executions were cancelled due to various court rulings.
Arkansas plans to put to death three more men before the end of the month.
Lee's lawyer, Nina Morrison, denounced the state's timeline, saying it "denied him the opportunity to conduct DNA testing that could have proven his innocence".
"While reasonable people can disagree on whether death is an appropriate form of punishment, no one should be executed when there is a possibility that person is innocent," she said in a statement.
The other inmate due to die on Thursday has been given a stay to make time for advanced DNA testing that his lawyers say could prove his innocence.
Stacey Johnson was convicted of the murder of Carol Heath, who was beaten and had her throat slit in her flat in 1993.
Thursday saw a flurry of legal activity, with the new Supreme Court Justice Neil Gorsuch siding with conservatives in the 5-4 decision to reject the inmates' claim that the accelerated process amounted to "cruel and unusual punishment".
It followed Arkansas's Supreme Court's overturning of a ruling by a lower court that blocked the use of the drug vecuronium bromide.
The McKesson Corporation, which supplied the drug, had accused the Arkansas Department of Correction of failing to say it planned to use the drug for executions.
Like many US states, Arkansas has struggled to find the drugs it needs to carry out executions. Its last was in 2005.
What did all these men do?
Bruce Ward - Strangled teenage shop clerk Rebecca Doss
Don Davis - Condemned for the execution-style killing of Jane Daniel as he burgled her home
Stacey Johnson - Murdered Carol Heath, who was beaten, strangled and had her throat slit
Ledell Lee - Bludgeoned Debra Reese to death with a tyre iron her husband had given her for protection
Jack Jones - Condemned for the rape and murder of accounts clerk Mary Phillips, and the nearly fatal beating of her 11-year-old daughter
Marcel Williams - Raped and murdered Stacey Erickson, after kidnapping her from a convenience store
Kenneth Williams - Murdered farmer Cecil Boren during an escape from prison where Williams had been incarcerated for murdering cheerleader Dominique Hurd