TALLAHASSEE, Fla.—Louis Bernard Gaskin, known as the “ninja killer,” is set to be executed on Wednesday for the 1989 slayings of a couple visiting the state from New Jersey.

Gaskin, 56, was scheduled to be executed at 6 p.m. by lethal injection for the deaths of Robert Sturmfels, 56, and Georgette Sturmfels, 55, on Dec. 20, 1989, in their Flagler County winter home on Florida’s northeast coast.

Gaskin, who was dubbed the “ninja killer” because he wore all-black ninja clothing during the crimes, shot his victims with a .22-caliber rifle, investigators said. He was convicted of first-degree murder.

Property that he stole from the Sturmfels’ home—a clock, two lamps, and a videocassette recorder—was found at his residence and were intended to be Christmas gifts for his girlfriend, according to investigators. He was also convicted of armed robbery, burglary, and the attempted murder of another couple who lived nearby that same night.

Local media reported at the time that Gaskin quickly confessed to the crimes and told a psychologist before his trial that he knew what he was doing.

“The guilt was always there,” Gaskin said. “The devil had more of a hold than God did. I knew that I was wrong. I wasn’t insane.”

Jurors voted 8–4 in 1990 to recommend the death sentence, which the judge accepted.

The state and U.S. supreme courts have rejected appeals Gaskin filed since his death warrant was signed, with the latest denial coming Tuesday.