JACKSON, Miss. — Edgar Ray Killen, a former Ku Klux Klan leader who was convicted in the 1964 'Mississippi Burning' slayings of three civil rights workers, has died in prison at the age of 92, the state's corrections department announced Friday.

The one-time Klan leader was serving a 60-year prison sentence for manslaughter when he died at 9 p.m. Thursday night inside the Mississippi State Penitentiary. An autopsy was pending, but no foul play was suspected, the corrections' statement said.

Edgar Ray Killen in Philadelphia, Mississippi on June 20, 2005. Rogelio V. Solis / AP file

His conviction came 41 years to the day after James Chaney, Michael Schwerner and Andrew Goodman, all in their 20s, were ambushed and killed by Klansmen. The three Freedom Summer workers had been investigating the burning of a black church near Philadelphia, Mississippi. The slayings shocked the nation, helped spur passage of the landmark Civil Rights Act of 1964 and were dramatized in the 1988 movie "Mississippi Burning."

The part-time preacher and lumber mill operator was 80 when a Neshoba County jury convicted him of three counts of manslaughter on June 21, 2005, despite his assertions that he was innocent of the killings. Killen was the only person ever to face state murder charges in the case.

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In a 2014 interview with The Associated Press inside the Mississippi State Penitentiary, Killen wouldn't say much about the 1964 killings. He said he remained a segregationist who did not believe in racial equality, but contended he harbored no ill will toward blacks. Killen said he never had talked about the events that landed him behind bars, and never would.

Long a suspect in the 1964 slayings, Killen had made a livelihood from farming, operating his sawmill and preaching to a small congregation at Smyrna Baptist Church in Union, south of Philadelphia, Mississippi.

On June 29, 1964, the FBI began distributing these pictures of civil rights workers, from left, Michael Schwerner, 24, of New York, James Chaney, 21, from Mississippi, and Andrew Goodman, 20, of New York. FBI via AP

According to FBI files and court transcripts from a 1967 federal conspiracy trial, Killen did most of the planning in the ambush killings of the civil rights workers. According to testimony in the 2005 murder trial, Killen served as a kleagle, or organizer, of the Klan in Neshoba County and helped set up a klavern, or local Klan group, in a nearby county.

Nineteen men, including Killen, were indicted on federal charges in the 1967 case. Seven were convicted of violating the victims' civil rights. None served more than six years.

Killen's federal case ended with a hung jury after one juror said she couldn't convict a preacher. During his state trial in 2005, witnesses testified that on June 21, 1964, Killen went to Meridian to round up carloads of Klansmen to ambush Schwerner, Chaney and Goodman, telling some of the Klan members to bring plastic or rubber gloves.

Witnesses said Killen then went to a Philadelphia funeral home as an alibi while the fatal attack occurred. The three bodies were found 44 days later, buried in a red-clay dam in rural Neshoba County.

In February 2010, Killen sued the FBI, claiming the government used a mafia hit man to pistol-whip and intimidate witnesses for information in the case. The federal lawsuit sought millions of dollars in damages and a declaration that his rights were violated when the FBI allegedly used a gangster known as "The Grim Reaper" during the investigation. The lawsuit was later dismissed.

Reputed Ku Klux Klan member Edgar Ray Killen in court on Jan. 7, 2005, in Philadelphia, Mississippi. Rogelo Solis / AP file

In the 2014 AP interview, Killen repeated his contention that he was not a criminal, but a political prisoner. Of one thing he was certain: "I could have beat that thing if I'd had the mental ability."

In the four-hour interview, he spoke of associations with hundreds of people during his life — from political figures to friends and neighbors. He was talkative about corruption in the Mississippi prison system, his good times and close relationship with the late Sen. James O. Eastland and his preaching at a tiny Baptist church in east Mississippi from which he got the nickname "Preacher."

Killen said people at Parchman were well aware of his identity before he arrived: "Oh yes. They knew who I was," he said.