Johnny Cash’s “Folsom Prison Blues” sure sounds prescient right now. After a “major riot” at California’s Folsom State Prison on Friday landed seven inmates in a local hospital, officials are working to discover what exactly caused the altercation. “At this point we have reviewed some of our surveillance tapes and all we’ve been able to gather it just erupted at once,” a spokesman said. Prison staff initially reacted to the outbreak by “using chemical agents,” he continued, but eventually deployed rubber bullets and, when that didn’t work, opened fire. Of the 200 prisoners involved in the fracas, five received gunshot wounds, though none of them were life-threatening. No prison guards were injured.