COLUMBIA, S.C. — Rita Bixby, who was serving a life sentence for planning a 2003 ambush on her property that killed two officers, died Monday in prison, just one week after her husband, who was accused of carrying out the ambush with their son. She was 79. He was 82.

Rita Bixby died of natural causes about 4 a.m. at Graham Correctional Institution, a prison in Columbia for women with special needs, said Richland County Coroner Gary Watts. He said Bixby had cancer, though he didn’t immediately what type.

A jury found Bixby guilty in October 2007 of conspiracy and two counts of accessory.

In July 2008, a judge ordered her husband, Arthur, to be committed to a mental institution, after a separate judge found he was unfit to stand trial for murder due to dementia.

The director of the New Hampshire funeral home handling the service for both Bixbys confirmed Monday that Arthur Bixby died Sept. 5 in Columbia. Arrangements have not been completed, said Bryan Gould of Ricker Funeral Home in Woodsville, N.H.

The Bixbys’ son, Steven Bixby, was sentenced to death for killing Abbeville County Sheriff’s Sgt. Danny Wilson and Constable Donnie Ouzts. The state Supreme Court upheld his death sentence last year. The 44-year-old Bixby is on death row at Lieber Correctional Institution in Ridgeville, about 90 miles southeast of Columbia.

“It’s sad so many lives have been ruined,” Solicitor Jerry Peace, the chief prosecutor for four counties including Abbeville, said about the Bixbys’ deaths.

Last month, the Court of Appeals denied Rita Bixby’s arguments that four letters her son wrote from prison, and separate conversations he had with two women before the shootout, should not have been used in her prosecution. Her lawyer had asked the court to reconsider her appeal.

Public defender Elizabeth Franklin-Best said if the appeals court declined, she’d planned to ask the state Supreme Court to review the case. She contends the conversations and letters should not have been allowed at trial. She was unsure Monday how to proceed in the wake of her client’s death.

“I have to weigh my options and see what I should do,” Franklin-Best said.

The Bixby family became angry when highway workers started putting survey stakes in their yard to begin a widening project that took away about 20 feet of their land. State Department of Transportation officials showed the family documents proving they had the rights to the property, but the family couldn’t find the information on their own and didn’t trust the government, their attorneys said.

Rita Bixby wasn’t home at the time of the shootings, but prosecutors said she planned the ambush on the next law officer to come to their home and took their disabled son away for his own safety.

Wilson, who was sent as a mediator, was shot Dec. 8, 2003, while standing on the front porch of the Bixby home, and was dragged inside. Ouzts, who arrived to check on Wilson, was shot in the back as he stepped out of his patrol car.

The shootings sparked a daylong gun battle with police. Officers were able to remove Ouzts, but he died on the way to the hospital. Wilson died of blood loss while handcuffed inside the Bixby home.

Arthur Bixby, who was also charged with killing the officers, was wounded in the standoff that finally ended after hundreds of rounds were exchanged.

In Steven Bixby’s prison letters, also used earlier in his death penalty case, he described how he took Wilson’s gun, handcuffed the dying man, dragged him inside the house and read him Miranda rights. The letters also give his explanation for shooting the officers, reference statements between him and his father, and allude to pre-standoff conversations he had with a former girlfriend.

The Bixbys moved to South Carolina from New Hampshire in the 1990s after participating in a group angry with zoning laws and taxes.

While living in Warren, N.H., in the early 1980s, the Bixbys had run-ins with a judge that were deemed so threatening she was given round-the-clock security. The family’s contempt for state Supreme Court Chief Justice Linda Dalianis, then a Superior Court judge, grew after she ordered Arthur Bixby jailed in 1981 for failing to pay a judgment on a three-year-old lawsuit. The case stemmed from an unpaid bill for $850. Bixby had told Dalianis he had no intention to make payment.