Alabama executed a 46-year-old man on Thursday for the 1994 murders of three fast-food workers during a late-night robbery, in the 13 execution this year in the United States.

Alabama put Robert Melson to death by lethal injection at 10:27 p.m. local time at its death chamber in Atmore. It was the second execution in Alabama in 2017.

Melson made no last statement and there were no complications with the execution, prison spokesman Bob Horton said.

Melson was convicted of murdering James Nathaniel Baker, 17, Darryl Collier, 23 and Tamika Collins, 18, during a robbery at a fried chicken fast food restaurant in Gadsden, about 115 miles northwest of Montgomery.

"It is my prayer that, with tonight’s events, the victims’ families can finally have closure," Alabama Governor Kay Ivey said in a statement.

As the restaurant was closing at about midnight, Melson and another robber forced four employees to remove cash from the restaurant safe and then ordered them into a freezer, court documents said.

Melson fatally shot three of the workers while the fourth, Bryant Archer, was shot multiple times but survived, the documents said.

Archer identified one of the robbers as Cuhuatemoc Peraita, a former employee at the restaurant, but did not know the shooter, they said. Police later linked Melson to Peraita, who was 17 at the time of the killings and too young to be executed under U.S. law.

Peraita was sentenced to life without parole. While in prison, he killed another inmate and currently is on death row, according to court records.

Lawyers for Melson tried to halt his execution, arguing a drug in the state's lethal injection has been linked to troubled executions in Alabama, Arizona and Oklahoma, where inmates could be seen twisting on death chamber gurneys. They said its use violated constitutional protections against cruel and unusual punishment.

The lawyers contend the drug, the sedative midazolam, does not render a person sufficiently unconscious for surgery and should not be used in executions where it is typically followed by a drug that halts breathing and another that induces cardiac arrest.

Last week, a federal appeals court in Atlanta issued a stay of execution for Melson because of the drug issue.

Alabama appealed and the U.S. Supreme Court on Tuesday lifted Melson's stay, allowing the execution to proceed on Thursday.

(Reporting by David Beasley; Additional reporting by Alex Dobuzinskis in Los Angeles and Jon Herskovitz in Austin; Editing by Bill Trott, Jonathan Oatis and Michael Perry)