Two years after the IDD opened, a riot took the lives of a guard and an inmate, and numerous others suffered injuries. . . most guards had been working double 12-hour shifts fighting a forest fire on the mountain ridge behind the institution. A few inmates had complained about abbreviated recreation privileges while the officers were occupied with the fire, but there was no reason to suspect trouble.

Only 15 fatigued guards, armed with "slender canes," were in the mess hall on July 23, 1923, supervising 400 inmates. "The meal had scarcely been served," according to the New York World, when Philip Sasso, "[an inmate] of giant stature ... leaped upon a stool and hurled a bowl against the wall. Immediately the hall was a confused mass of scrambling, shouting men. . . ."

While guard Jesse Christian struggled with one assailant, Sasso crashed a heavy, wooden stool over the guard's head. Christian fell and rolled under a table, his skull fractured. He died the next morning.

One guard managed to flee the hall to Dr. Thayer's office. As the "surging wave of enraged" inmates, still raining missiles, backed the huddled guards into a corner, Sasso and inmate Leo Shepherd started for the exit, shouting for the others to follow. At the door, they met Thayer and Chief Officer Robert Wager. Thayer leveled a revolver at the two inmates and made them put up their hands. The surrender of the leaders cowed the others, who were herded into small groups and taken to the cellblock.

Sasso was taken to an isolated cell in the basement. Shepherd, identified with Sasso as a ringleader, was also being led downstairs to the dungeon, with one guard in front and three behind him, when, according to the guards, he leaped for the guard in front. The guard "dodged quickly, throwing Shepherd heavily into the concrete wall." Shepherd died a few minutes later; an autopsy showed that two fractured ribs had punctured his lung.

Sasso was convicted of Murder, 2nd degree, and received a life sentence to prison. Other inmates taking part were "punished and transferred." The heavy wooden stools that served as deadly weapons were replaced by solid square benches that encircled the tables.