Edgar Ray Killen, the former Klansman who was sentenced to a 60-year prison term in 2005 for arranging the murders of three young civil rights workers outside Philadelphia, Miss., in 1964 during the Freedom Summer drive to register Southern black voters, died on Thursday night in prison in Parchman, Miss. He was 92.

The Mississippi corrections department said he was pronounced dead at the hospital at the Mississippi State Penitentiary at 9 p.m. No cause was given, but the department said he had been treated for congestive heart failure and hypertension.

Mr. Killen was convicted of state manslaughter charges 41 years to the day after James Earl Chaney, 21, a black man from Meridian, Miss., and two white New Yorkers, Andrew Goodman, 20, and Michael Schwerner, 24, disappeared in a death trap set by a local deputy sheriff and a gang of his fellow Ku Klux Klansmen.

He was prosecuted in one of the South’s major “atonement” trials, in which the Mississippi authorities revisited civil rights-era atrocities. He was convicted of a crime that galvanized the civil rights movement, stamped the town of Philadelphia as an outpost of terror and inspired the 1988 Hollywood movie “Mississippi Burning,” directed by Alan Parker.