A Mississippi man who was executed for shooting dead his estranged wife admitted just before he died to also killing his sister-in-law, authorities revealed on Monday.

David Neal Cox, 50, told his attorneys he killed his sister-in-law Felicia Cox in 2007 and provided details on where her remains could be found before he was executed on Nov. 17 over the 2010 slaying of his wife.

District Attorney John Weddle said at a news conference on Monday that Cox had been a longtime suspect in his sister-in-law’s disappearance.

Weddle would not disclose the exact location Cox provided but said investigators were preparing to search in Pontotoc County where Felicia was last seen.

Felicia vanished after she went to visit Cox’s estranged wife, Kim Kirk Cox, in Pontotoc in July 2007.

Mississippi State University archaeology and anthropology experts are on hand to assist if the remains are located, Weddle said.

“We would like to stress that locating the remains of Felicia Cox is not a foregone conclusion,” Weddle added. “We are hopeful that the information is accurate and that recovery efforts will be successful so that Felicia’s family may give her a proper burial.”

Authorities haven’t released any details on how Felicia was killed, or the circumstances leading up to her death.

Cox admitted to killing Felicia to his attorneys prior to execution and waived his attorney-client privilege after death, Weddle said.

The disclosure was relayed to Weddle’s office two days after Cox was put to death.

Mississippi’s Office of Capital Post-Conviction Counsel issued a statement on Monday saying Cox had “felt deep remorse and wanted to bring closure” to his sister-in-law’s family.

Cox was executed at the Mississippi State Penitentiary over the fatal shooting of his wife in May 2010.

He pleaded guilty to killing Kim and also sexually assaulting his then-12-year-old stepdaughter as her mother died.

Prior to his execution date being set, Cox abandoned all appeals and filed paperwork declaring himself “worthy of death.”

He was the first inmate to be executed in Mississippi in nine years.

With Post wires