The decision by Solicitor Jerry Peace came a day after a circuit judge ruled that Arthur Bixby can't stand trial because he has dementia.
Instead of pursuing the original death penalty case, Peace said he will now ask a probate court judge to have Bixby committed indefinitely, something the prosecutor said he hopes will bring at least some closure to the families of the two men gunned down outside the Bixby family home nearly five years ago.
Peace says Bixby could be tried later if he were to become competent.
"Even though he stays committed and institutionalized, there's no finality about his role in this whole episode," said Peace, who said he will make the request later Tuesday. "This has been a long road for the family, and I hope I never have another case that wings its way through the system like this."
Phone numbers for the officers' families could not immediately be found to reach them for comment.
The patriarch of the Bixby family, which relocated to South Carolina from New Hampshire, would have been the final family member to stand trial in the Dec. 8, 2003, shooting deaths of sheriff's Sgt. Danny Wilson and state Constable Donnie Ouzts.
Authorities said Bixby and his son, Steven, ambushed the officers over a land dispute with Department of Transportation workers, who were starting on a road-widening project outside their home.
The shootings marked the beginning of a 14-hour standoff and shootout with more than 100 officers in Abbeville, about 85 miles west of Columbia.
Wilson went to the home to discuss the Bixbys' anger over the road project, only to be mowed down while standing on the front porch, his body dragged inside. Ouzts, who arrived later to check on Wilson, was shot as he stepped out of his patrol car and died on the way to the hospital.
The case attracted national attention in the years between the shootings and Steven Bixby's 2007 trial, with property rights advocates posting messages on Internet sites in support of the family's right to defend the 20 feet of land the state wanted for a road expansion.
In letters released during his trial, jurors heard how Bixby wrote to an ex-girlfriend from jail that he believed the shootings were justified.
"The laws were made to protect us from the police," Bixby wrote, calling the shootings "right and correct in God's eyes."
Steven Bixby, 40, was sentenced to death in February 2007 for the shootings. Several months later, his mother, 75-year-old Rita Bixby, was sentenced to life in prison for knowing what her son and husband planned but not telling authorities.
Both Steven and Rita Bixby are appealing their sentences. Larry Crane, Arthur Bixby's attorney, was in court Tuesday morning and did not immediately respond to a phone message at his office.