This file photo provided by the Nebraska Department of Correctional Services shows death-row inmate Carey Dean Moore. Nebraska prison officials are preparing to execute Moore on Aug. 14, 2018, for the 1979 murders of two Omaha cab drivers. (Photo: AP) 
 
 Nebraska executed Carey Dean Moore on Tuesday morning in the state’s first death by lethal injection. 
 
 Moore, 60, had served 38 years on death row for shooting and killing cab drivers Reuel Van Ness and Maynard Helgeland in the summer of 1979, according to the Omaha World-Herald. He had said he was ready to die. 
 
 “We could see him mouthing some words toward his witnesses, it was clear he said I love you several times," witness Brent Martin of Nebraska Radio Network said at a news conference after the death, KLKN-TV in Lincoln, Nebraska, reports. 
 
 The fatal drug cocktail used for Moore’s execution had never been used to put a person to death, the Lincoln Journal Star reports. The concoction included sedative diazepam, muscle relaxant cisatracurium, potassium chloride and fentanyl. 
 
 Fentanyl is an opioid painkiller that is 30 times more potent than heroin and at least 80 times stronger than morphine, according to the Drug Enforcement Administration (DEA). Nearly 30,000 overdose deaths were linked to fentanyl in 2017, according to Centers for Disease Control and Prevention data cited by the National Institute on Drug Abuse. 
 
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 The drug mixture is controversial, because if the substances did not work as planned, Moore could have suffered extreme pain. Friday, a lawyer for the drug company behind the paralyzing drug said it might not be effective if it wasn’t stored at the proper temperature, the World-Herald reports. 
 
 Witnesses reported no complications, only some coughing before Moore stopped moving. Moore died at 10:47 a.m. CT surrounded by three people, a clergy member and four media member witnesses, according to KLKN. 
 
 Moore released a "last statement," where he apologized to his brother, Donald, who was with him during his first murder. 
 
 "I am terribly sorry," Moore wrote. "Please forgive me, Don, somehow." 
 
 Monday, the American Civil Liberties Union of Nebraska filed a motion to delay Moore’s execution on behalf of eight death row inmates, KETV-TV, in Omaha, Nebraska, reports. After the execution, ACLU of Nebraska Executive Director Danielle Conrad condemned the decision. 
 
 "This execution of Carey Dean Moore does not comport with Nebraska’s proud tradition of open government," Conrad said in a statement Tuesday. "Today stands as the most recent dark chapter in Nebraska's troubled history with the death penalty." 
 
 In 2016, Nebraska reinstated the death penalty. Before Moore, the state had executed 37 people, the last being killed by an electric chair. 
 
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 Follow Ashley May on Twitter: @AshleyMayTweets 
 
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 LINCOLN, Neb. — Prison officials in Nebraska used the powerful opioid fentanyl to help execute a convicted murderer on Tuesday, the first such use of the drug in the United States and the first execution in the state since voters overturned a death penalty ban in 2016. 
 
 The use of fentanyl, an opioid at the heart of the nation’s overdose crisis, as part of a previously untested four-drug cocktail drew concern from death penalty experts who questioned how the execution unfolded. And here in Nebraska, a state that last killed a prisoner in 1997, the lethal injection represented a stark political turnabout from when legislators outlawed capital punishment three years ago. 
 
 The condemned man, Carey Dean Moore, 60, had been convicted of killing two Omaha taxi drivers decades ago and did not seek a reprieve in his final months. He was pronounced dead at 10:47 a.m. at the Nebraska State Penitentiary, officials said, 23 minutes after the first drug was administered. Mr. Moore breathed heavily at one point and coughed, said four Nebraska journalists whom the state selected to watch the execution. Mr. Moore’s face turned red, then purple. 
 
 The four-drug cocktail contained diazepam, a tranquilizer; fentanyl citrate, a powerful synthetic opioid that can block breathing and knock out consciousness; cisatracurium besylate, a muscle relaxant; and potassium chloride, which stops the heart.
– For the first time, fentanyl has been used in the execution of a US prisoner. Carey Dean Moore was put to death via lethal injection at the Nebraska State Penitentiary Tuesday morning using a previously untested combination of four drugs: fentanyl citrate, the powerful synthetic opioid blamed for deadly overdoses as the nation struggles with an opioid epidemic; the tranquilizer diazepam; the muscle relaxant cisatracurium besylate; and potassium chloride to stop the heart. "We really don’t know how fentanyl is going to play out in an execution, as opposed to an opioid overdose," a law professor told the New York Times in advance of the execution. "Simply because people are dying as a result of fentanyl doesn’t mean they’re dying in a way that would be considered acceptable as a form of execution." Moore, 60, was convicted of killing two taxi drivers in 1979, and while he did not seek a last-minute reprieve from his sentence, two pharmaceutical companies did attempt to block the execution, arguing their reputations would be harmed. But prison officials wouldn't identify the suppliers of the drugs, so since the companies couldn't prove their products were being used, the execution—Nebraska's first since 1997—was allowed to proceed. According to USA Today, witnesses reported no apparent complications beyond some coughing by Moore. He reportedly said "I love you" several times before dying. The four-drug cocktail that was used could offer a new execution method to states that are struggling to obtain execution drugs, but the inclusion of fentanyl has raised ethical concerns. (Another execution that planned to use fentanyl was halted in Nevada.)