Charles Rhines was executed by lethal injection at 7:39 p.m., after the U.S.
Supreme Court declined to halt the execution despite three late appeals.
"Ed and Peggy Schaeffer, I forgive you for your anger and hatred toward me," Rhines said, before thanking his defense team.
Rhines, 63, ambushed 22-year-old Donnivan Schaefer in 1992 when Schaefer surprised him in the midst of burglarizing a Rapid City doughnut shop where Schaeffer worked.