The Lynching: The Epic Courtroom Battle That Brought Down the Klan by Laurence Leamer:
Chambliss had built many bombs before, but at the church the detonator apparently misfired, and the bomb did not go off in the middle of the night when no one was in the building. Instead, at 10:22 A.M. on Sunday, September 15, 1963, the large bomb destroyed a corner of the church, killing four girls: fourteen-year-old Addie Mae Collins, Carole Robertson, and Cynthia Wesley, and eleven-year-old Denise McNair; twenty-two others were injured.
The explosion sent a wave of flames streaking above the church, filling the building with smoke and debris. Out on the street, it blew a driver out of his car. It was the worst single act of violence in the history of the modern civil rights movement.