Around 9 AM on Saturday, July 22, 1978, about 500 inmates were returning to their cells in the North Cellhouse at Pontiac when a riot erupted resulting in the deaths of three staff. Seventeen inmates were charged with the murders of Correctional Officers Robert J. Conkle, 22, Stanley Cole, 47, both of Pontiac, and Lieutenant William N. Thomas, 49, of Saunemin.

None of the inmates charged in the brutal murders were convicted. Thomas and Conkle were stabbed with shanks numerous times shortly after the riot began near a doorway into the North Cellhouse; Cole was stabbed with a screwdriver on the top floor of the four story building.

Inmates set fires to several buildings in the complex resulting in an estimated $4 million in damage. Pontiac staff and Illinois State Police Troopers returned inmates to their cells by 8 PM; three inmates received minor injuries.

Conjecture as to why the inmates rioted has been speculated on for two decades - was it the 92 degree heat, gangs retaliating against strict security staff, crowding, or an attempt to kill Warden Thaddeus Pinckney?