Daniel Lewis Lee, 47, of Yukon, Oklahoma is convicted of torturing and killing a family in Arkansas in 1996, and later dumping their bodies in a lake.

He was killed by lethal injection at the federal prison in Terre Haute, Indiana.

“I did not do it. I have made a lot of mistakes in my life, but I’m not a murderer,” he said just before execution

His final words were: "You’re killing an innocent man.”

The decision to move forward with the execution -- the first by the Bureau of Prisons since 2003 -- drew scrutiny from civil rights groups and the relatives of Lee’s victims, who had sued to try to halt it, citing concerns about the coronavirus pandemic.

The pandemic has killed more than 135,000 people in the US and is ravaging prisons nationwide.

Critics argued that the government was creating an unnecessary and manufactured urgency for political gain.

“The government has been trying to plow forward with these executions despite many unanswered questions about the legality of its new execution protocol,” said Shawn Nolan, one of the attorneys for the men facing federal execution.

The execution of Lee, who was pronounced dead at 8:07 a.m. EDT, went off after a series of legal volleys that ended when the Supreme Court stepped in early Tuesday in a 5-4 ruling and allowed it to move forward.

Attorney General William Barr has said the Justice Department has a duty to carry out the sentences imposed by the courts, including the death penalty, and to bring a sense of closure to the victims and those in the communities where the killings happened.

But relatives of those killed by Lee in 1996 strongly opposed that idea and long argued that Lee deserved a sentence of life in prison. They wanted to be present to counter any contention that the execution was being done on their behalf.

Executions on the federal level have been rare, and the government has put to death only three defendants since restoring the federal death penalty in 1988 — most recently in 2003, when Louis Jones was executed for the 1995 kidnapping, rape and murder of a young female soldier.

Though there hadn’t been a federal execution since 2003, the Justice Department has continued to approve death penalty prosecutions and federal courts have sentenced defendants to death.

Numbers of state executions have fallen steadily since the last federal execution, according to data compiled by the Death Penalty Information Center. States put to death 59 people in 2004 and 22 in 2019, nine of which were in Texas.