HATTIESBURG, Mississippi (CNN) -- Former Ku Klux Klan Imperial Wizard Sam Bowers, who was twice tried during the 1960s in a firebombing that killed a black civil rights activist, was arrested again Thursday on charges of masterminding the crime.

Bowers, 73, was charged with murder and arson in the attack that killed Vernon Dahmer. Two carloads of Klansmen firebombed the Dahmer family home Jan. 10, 1966. Four Klansmen were convicted in the case; a fifth pleaded guilty.

The raid on the Dahmer home was in retaliation for Dahmer allowing black residents to pay their poll taxes at his store near Hattiesburg.

Two other men also were arrested Thursday. Charles Noble has been arrested on murder and arson charges. Deavours Nix is charged with arson.

Bowers stood trial during the late '60s -- once in state court, once in federal court -- but was set free when both juries deadlocked.

Officials said the renewed investigation in the long-dormant case has yielded new evidence they believe will mean a conviction this time. Prosecutors refused to detail the evidence but said it includes new witnesses.

"We want them to have a very, very speedy trial," Mississippi Attorney General Mike Moore said. "It's been 32 years and we think it's time justice is served."