As a recent spate of mass shootings has left many Americans grappling for answers, a new book about Columbine offers insight into the tragedy that all others has since been measured against. Salon editor Joan Walsh talks to author and Salon reporter Dave Cullen about his quest to explode the myths propagated in the aftermath of the shooting. Cullen discusses the failure of the police, and reflects on the ethical quandary he faced when he learned that Cassie Bernall had not, in fact, been killed because she said she believed in God (a falsehood that formed the basis of her mother’s bestselling memoir, “She said yes”).