Guards used pepper spray, rubber projectiles, and live ammunition to quell a huge riot at California's San Quentin prison yesterday. Prison authorities say between 150 and 200 inmates were involved in the riot in an exercise yard used by new arrivals, the Los Angeles Times reports. Dozens were slashed and stabbed by fellow inmates, and four of the most seriously injured were taken to outside hospitals. Three warning shots were fired from a semi-automatic rifle, but those bullets didn't cause any injuries. "When the inmates hear those live rounds going off, it brings them around," said a prison spokesman.