Texas death chamber
The death chamber in Huntsville, Texas, is seen on June 23, 2000. Joe Raedle/Newsmakers

A death row inmate who was executed in South Carolina is set to be quickly followed by four others across the U.S., marking a pace of death sentences carried out not seen in decades.

If the executions take place as scheduled, it will be the first time five inmates have been put to death in one week since 2003, the Associated Press reported, citing information from the nonprofit Death Penalty Information Center.

It would also push the total number of executions to 1,600 since the Supreme Court reinstated the death penalty in 1976, the center's executive director, Robin Maher, told AP.

"Two on a single day is unusual, and four on two days in the same week is also very unusual," Maher said, referring to the upcoming schedule.

University of Nebraska law professor Eric Berger, an expert on the death penalty and lethal injections, said the flurry of executions appeared to be an anomaly that resulted from each state setting dates around the same time after the inmates exhausted their appeals.

"I'm not aware of any reason other than coincidence," Berger said.

These are cases behind the potential chance occurrence:

South Carolina

Freddie Owens received a lethal injection Friday for the 1997 murder of a convenience store clerk during a robbery.

His execution was the state's first in 13 years and was delayed when prison officials couldn't get the three drugs they'd used in the past because pharmacies didn't want to be identified as the source.

The state adopted a new, one-drug protocol involving the sedative pentobarbital after lawmakers enacted legislation that allows officials to keep secret the identities of people or entities involved in planning or carrying out executions.

North Carolina also gives inmates the option of death by firing squad or electric chair, with the latter being the default method.

Texas

Travis Mullis, convicted of killing his 3-month old son in 2008, was scheduled to receive a lethal injection on Tuesday.

Mullis has a long history of mental illness and repeatedly sought to waive his right to appeal his death sentence.

His lawyers weren't planning to try to stay his execution.

Missouri

Marcellus Williams was also set to receive a lethal injection on Tuesday.

He was convicted of fatally stabbing a woman in 1998. His lawyers on Monday asked the state Supreme Court to stay his execution, citing alleged procedural errors during jury selection and the prosecution's alleged mishandling of the murder weapon.

But the court rejected the arguments and Gov. Mike Parson denied Williams' request for clemency.

Alabama

Alan Miller is set to become the second person executed in the U.S. with nitrogen gas.

Miller was convicted of killing three men during back-to-back workplace shootings in 1999.

In 2022, his scheduled execution was postponed when officials were unable to connect an intravenous line to administer a lethal injection.

Oklahoma

Also on Thursday, Emmanuel Littlejohn is scheduled to receive a lethal injection for fatally shooting a convenience store owner during a robbery in 1992.

Littlejohn admitted taking part in the holdup but claims he didn't fire the deadly shot.

Last month, the state Pardon and Parole Board voted 3-2 to recommend that Gov. Kevin Stitt grant him clemency but Stitt has yet to issue his decision.