An undated photo of Robert Bryant Melson. (Alabama Department of Corrections via AP)

Alabama executed inmate Robert Melson late Thursday for killing three people during a robbery at a Popeye’s restaurant in 1994.

Melson was pronounced dead at 10:27 p.m. local time, following a lethal injection at Holman Correctional Facility in Atmore, according to the Associated Press. The execution began at 9:55 p.m., not long after the U.S. Supreme Court denied a last-minute stay request.

It was the nation’s 13th execution this year, and the second in Alabama in 2017, Reuters reported.

Melson declined an opportunity to say a few words before the execution, according to AL.com:

When asked if he had any last words, Melson shook his head ‘no.’ For approximately seven minutes, Melson appeared to have slightly labored breathing. He did not respond to a consciousness check by a corrections officer before the second two drugs in the three-drug execution method — which stop the heart and breathing — were administered.

Melson had been convicted of multiple counts of capital murder, attempted murder and robbery.

State prosecutors said he and a former employee robbed the restaurant in Gadsden, about 60 miles northeast of Birmingham. Melson then fired into the restaurant’s freezer, killing three employees — Nathaniel Baker, Tamika Collins and Darrell Collier — and injuring worker Bryant Archer, the AP reported.

Archer identified one of the robbers — the former employee — as Cuhuatemoc Peraita, who was sentenced to life without parole, according to Reuters. He is currently on death row for killing an inmate while in prison.

Melson’s execution had been temporarily stayed Thursday to consider last-minute briefs offered by his attorney, who argued the state’s lethal injection methods were inhumane and violated the constitutional protections against cruel and unusual punishment, according to AL.com.

“Alabama’s execution protocol is an illusion. It creates the illusion of a peaceful death when in truth, it is anything but,” Melson’s attorneys wrote in the filing to the Alabama Supreme Court, noting previously laborsome executions in Alabama, Arizona and Oklahoma, the AP reported.

In December, an Alabama inmate struggled for more than 10 minutes during an execution after being given the sedative midazolam, the AP reported.

After Melson’s death, Alabama Attorney General Steve Marshall said in a statement that Melson’s “decades long avoidance of justice is over,” according to AL.com. “For twenty-three years, the families of the three young people whose lives he took, as well as a survivor, have waited for closure and healing.”