A man who was recently executed in Mississippi in relation to the murder of his estranged wife confessed to a separate killing just days prior his death, a prosecutor said Monday (December 6) via ABC News.

David Neal Cox, 50, reportedly told his attorneys he was responsible for the 2007 death of his sister-in-law, Felicia Cox, then 40, and gave detailed instructions on how to locate her remains ahead of his execution on November 17, according to John Weddle, the district attorney for several northern Mississippi counties.

Cox had been considered a longtime suspect in the 2007 cold case into his sister-in-law's disappearance and death prior to the death row confession.

“There is no indication that anyone other than Cox is responsible for Felicia Cox’s death,” Weddle told a news conference via ABC News.

The state's Office of Capital Post-Conviction Counsel issued a news release in relation to the confession on Monday (December 6), which stated that David Neal Cox "felt deep remorse and wanted to bring closure" to the family of Felicia Cox.

Weddle didn't specify details on where Felicia Cox's remains were said to be, but confirmed it was in Pontotoc County, Mississippi, where she was last reported to be seen prior to her disappearance.

The district attorney confirmed investigators were preparing to launch recovery efforts and Mississippi State University archaeology and anthropology experts will assist in the investigation if remains are located in the area.

“We would like to stress that locating the remains of Felicia Cox is not a foregone conclusion," Weddle added via ABC News. "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."

Felicia Cox was reported to have been seen last during a July 2007 visit to her sister-in-law, Kim Kirk Cox, who was married to David Neal Cox at the time and later murdered by him in May 2010, the crime he was executed for last month.

David Neal Cox filed court papers acknowledging himself as "worthy of death" prior to having his execution date scheduled by the Supreme Court.

Cox pleaded guilty to capital murder in 2010 in relation to the May 2010 shooting death of his wife, as well as several other charges, including sexual assault, before being handed down a death sentence.

Weddle confirmed Cox's confession in relation to the death of his sister-in-law was made in late October and the information was presented to the district attorney's office two days after Cox's execution.

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