A Florida inmate serving two life sentences for multiple murders has confessed to murdering six additional people in Pennsylvania in the 1970s. 

According to a Wednesday statement from Pennsylvania State Police (PSP), 79-year-old Edward A. Surratt "implicated himself in four unsolved PSP homicide investigations" when PSP investigators spoke with him in March at Florida's Raiford Correctional Facility.

The killings took place between 1977 and 1978.

In 1977, the former truck driver and Aliquippac, Pennsylvania resident murdered William and Nancy Adams in Beaver County; Guy and Laura Mills near Bedford; and Joel Krueger near McConnellsburg.

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In 1978, Surratt allegedly also killed John Shelkons, in Beaver County.

He had already faced charges in Shelkons’ death, but a judge dismissed them in 1980 due to his other convictions and the security risk of transporting him to Pennsylvania for trial, according to the Pittsburgh Post-Gazette.

Surratt has also been convicted of murder in South Carolina.

State police said that district attorneys in each county agreed not to prosecute Surratt for the cold-case homicides due to his life sentences in other jurisdictions.

This undated booking photo provided by the Florida Department of Corrections shows Edward Surratt. Surratt, a Florida inmate who admitted he killed six people in Pennsylvania in the 1970s also discussed five to seven other slayings in the state, and police in those areas have been alerted, an investigator said Thursday, June 3, 2021. (Florida Department of Corrections via AP)

"PSP investigators never stopped seeking justice for the victims of these terrible crimes and their families," Lt. Col. Scott Price, PSP deputy commissioner of operations, said in a statement. "We hope that the confessions announced today will help bring some semblance of closure to the victims' loved ones."  

However, The Associated Press reported on Thursday that Surratt had also discussed five to seven other slayings in Pennsylvania and that police in those areas have been alerted.

Investigators made contact with Surratt in 2018. 

Speaking with Fox News on Friday, PSP Trooper Joshua Black, an investigator on the case, recalled the effort – which has notably been stalled by the impact of the COVID-19 pandemic

"It started several years ago back in 2018 when we went to interview him about another homicide, which he did not take credit for because he had nothing to do with it. And then, after that, it was just keeping in touch with him over the course of the next several years, just keeping a rapport with him," Black said. 

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"The homicides that he discussed with us he was always the suspect in. There just wasn't – we didn't have the direct physical evidence to link into it. We had more circumstantial evidence," the investigator – a more than 13-year veteran of the agency – added. "So, we went down to specifically talk about those this time and he was able to confirm that he was responsible for those … We knew that he did it. We just didn't have enough to officially close the cases."

The family members of the victims have been notified of Surratt's confessions and the cases are no longer on the list of PSP cold cases that are actively investigated and updated at least twice every year.

The PSP investigator said the most important thing is that state police can "better utilize" resources to the "true whodunits and the ones that we're actively trying to solve, whether they're 5 years old or 50 years old." 

In 2007, Surratt told an interviewer he was involved in killings dating to the 1970s in Pennsylvania and Ohio

Ohio's Beaver Township Chief of Police Carl Frost told Fox News on Friday that Surratt had previously opened up because he had intended to move to a South Carolina prison. The state later denied his transfer. 

Frost had previously reopened the cold cases when he became a detective and remembered the killings. 

"Surratt's M.O. was rape; [it] was his motivating force. His M.O. was if there [weren't] children in the house, he would kill any threats – as in any men – and then he would rape the wife and then kill her there … If there were children in the home, he would kill the man and abduct the wife and kill her elsewhere – never bothered the kids … That was his pattern in all of them," he said, noting that there were exceptions for "weird ones" in Pennsylvania. 

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In watching Surratt's interview from 2007, Frost said the inmate had "no remorse" for his actions.

"The only reason he would be confessing is to try to finish out his years a little more comfortably, would be my opinion," he said.

"I look forward to the day that, hopefully, he'll sit down and just go right down the line and confess to every one of them that he did," Frost said. "He's probably the most prolific African American serial killer in U.S. history, I would say."

Surratt has been incarcerated since October 1978.

The Associated Press contributed to this report.