Lee, 51, was administered the lethal injection at 11:44 p.m. Thursday (12:44 a.m. ET). He was pronounced dead 12 minutes later.
His execution was Arkansas' first since 2005. The state had planned to execute eight inmates over 11 days starting April 17, saying its lethal-injection drugs will expire at the end of the month. Four of the men have received stays for various reasons.
Attorneys for the eight men attempted to block the executions, including using the argument that midazolam, the drug used to make inmates unconscious before two more drugs paralyze and kill them, does not effectively prevent a painful death.
The second drug, pancuronium bromide, paralyzes the inmate. The third, potassium chloride, brings on cardiac arrest and stops the heart.
"Unless the prisoner is unconscious, then drugs two and three will cause pain -- torturous punishment, in violation of the Eighth Amendment, and state guarantees against cruel and unusual punishment," said Jeffrey Rosenzweig, an attorney for three of the inmates.
The lawyers have also fought the state's decision to conduct the series of executions in a short time frame, which the state has said is because its lethal-injection drugs will expire at the end of the month.
"No state has ever conducted eight executions" over an 11-day period, according to Robert Dunham, executive director of the Death Penalty Information Center.
One of the drug companies was granted a restraining order
after arguing in court that their drug wasn't supposed to be used for capital punishment.
McKesson Medical Surgical Inc. argued its vecuronium bromide was intended only for medical purposes, not executions, and that the Arkansas Department of Corrections "misled" the company
when it purchased the drug, according to a court brief.
"ADC (the Arkansas Department of Correction) personnel used an existing medical license, which is to be used only to order products with legitimate medical uses, and an irregular ordering process to obtain the vecuronium via phone order with a McKesson salesperson," the brief said.
The Arkansas Supreme Court later reversed the restraining order.
Two other inmates -- Jack Harold Jones and Marcel W. Williams, both sentenced to death for capital murder -- are scheduled to be executed Monday.
Thirty-one states currently administer the death penalty, and lethal injection is the primary means of execution in all of them. The number of executions carried out in the United States fell to a 25-year low in 2016.
Lee was convicted in 1995
in the murder of Debra Reese, 26, two years prior. Reese was found dead in her home in Jacksonville, Arkansas, where she had been strangled and beaten with a small wooden bat her husband had given her for protection.
Several of Reese's neighbors saw Lee near the house and identified him to police.
Before Lee's death, all executions were put on hold in the state after a judge issued a restraining order on a key lethal injection drug.
His execution followed a flurry of court rulings Thursday, capped by the US Supreme Court's denial of multiple requests for stays of execution.
"Today is a shameful day for Arkansas, which is callously rushing the judicial process by treating human beings as though they have a sell-by date," Amnesty International said in a statement.
"While other states have increasingly come to the conclusion that the capital punishment system is beyond repair, Arkansas is running in the opposite direction from progress. This assembly line of executions must stop and this cruel and inhuman punishment should be ended once and for all."
At one point on Thursday night, the United States Supreme Court briefly delayed the execution as it reviewed appeals. It then voted to allow the state to proceed with the execution.
About 30 minutes after the high court's ruling, Lee was pronounced dead.
No final words
Just before Lee was put to death, officials at the Cummins Unit prison in Grady, Arkansas, asked him twice for his final words, but he did not respond. His last meal was Holy Communion.
At 11:44 p.m., Lee was given the lethal injection. His eyes closed three minutes later. He did not appear to show signs of discomfort, according to Sean Murphy, a reporter with the Associated Press who attended the execution as one of three media witnesses.
"A member of the execution team began a consciousness check at 11:49 p.m. by flicking (Lee's) head, rubbing his eyes and tapping his sternum. Then at 11:55 p.m. his heart was checked with a stethoscope," Murphy said.
Lee was officially pronounced dead one minute later.