One of perpetrators of a particularly infamous hate crime during the civil rights movement died in prison Thursday. Edgar Ray Killen, who was convicted for involvement in the 1964 killings of three civil rights workers in Mississippi, died at the Mississippi State Penitentiary, the Associated Press reported.

Killen, 92, was serving three consecutive 20-year terms at the facility, the Los Angeles Times reported. Foul play was not suspected in the former Ku Klux Klan leader’s death.

He was a farmer, preacher and sawmill operator in Mississippi during the height of the civil rights movement of the 1960s. In 2005, he was convicted of manslaughter for the 1964 deaths of Michael Schwerner, James Chaney and Andrew Goodman outside Philadelphia, Mississippi.

The three men were investigating the burning of a black church in the area that summer when their station wagon stopped by local police on the night of June 21, according to a detailed account of the incident on PBS. They were held for several hours for speeding charges before eventually being released that night, never to be seen again until their bodies were discovered that August.

A lengthy and dramatic FBI investigation followed by a highly publicized trial found seven men guilty of involvement in the mens’ deaths, but nobody served more than six years in prison. It was not until 2005 that Killen was charged with murder by a grand jury after new information related the case emerged. Killen was not found guilty of murder, but was found guilty of organizing Klansmen to ambush and ultimately kill the three men after they left the police station that night in 1964.

The events of that night in Mississippi inspired the critically acclaimed 1988 film “Mississippi Burning,” starring Gene Hackman and Willem Dafoe.