A man accused of killing an off-duty prison guard who had agreed to give him and another man a ride outside a Georgia Walmart store is scheduled to be executed later this month.

Marion Wilson Jr., 42, is set to die June 20 at the state prison in Jackson, state Attorney General Chris Carr said in a news release Wednesday. Wilson and Robert Earl Butts Jr. were convicted of murder and sentenced to death in the March 1996 slaying of Donovan Corey Parks in Milledgeville, about 90 miles (145 kilometers) southeast of Atlanta.

Butts' lawyers had argued that Wilson killed Parks, while Wilson's lawyers have said Butts fired the fatal shot.

Wilson was convicted in November 1997 of malice murder, armed robbery, hijacking a motor vehicle, possession of a firearm during the commission of a felony and possession of a sawed-off shotgun. Butts was found guilty of the same charges about a year later.

The state executed Butts in May 2018.

Wilson's attorneys have argued his constitutional rights were violated because his trial lawyers didn't fully investigate his background and failed to present evidence that could have convinced jurors not to sentence him to death. But state and federal courts have rejected those arguments.

Parks went to Walmart to buy cat food on March 28, 1996, leaving his car right out front, and witnesses saw Wilson and Butts standing behind him in a checkout line. One witness heard Butts ask Parks for a ride, and several saw them getting into Parks' car, according to a Georgia Supreme Court summary of the evidence and testimony presented at trial.

Butts was in the front passenger seat and Wilson was in the back as they left the parking lot. Parks' body was found lying face down on a nearby residential street a short time later, the summary says.

Police made note of the vehicles in the Walmart parking lot, and Butts' vehicle was among those that remained overnight. Wilson was arrested based on statements from witnesses at Walmart, and investigators found a sawed-off shotgun with the same type of ammunition used to kill Parks at Wilson's home, the summary says.

Wilson made statements to investigators and rode with them to point out stops he and Butts had made after Parks was killed, the summary says.

Wilson told investigators that Butts had pulled out a sawed-off shotgun, ordered Parks to drive and then ordered Parks out of the car and shot him once in the back of the head, the summary says.

Butts and Wilson then drove to a service station in Gray, where Wilson was seen by witnesses and recorded by a security camera, and put gas in Parks' car. Then they drove to Atlanta to try to sell the car. Unsuccessful, they bought two cans of gasoline, drove to Macon and set the car on fire, the summary says. They walked to a nearby public phone where Butts called his uncle to arrange a ride back to the Walmart to get Butts' car.

Authorities said Butts and Wilson were gang members, and among the items found at Wilson's house were three notebooks of handwritten gang "creeds," secret alphabets and symbols, as well as a photo of a young man making a gang hand sign, the summary says.

Wilson would be the second prisoner executed by Georgia this year.