On April 20, 1999, students at Columbine High School ran for their lives. In the hours that followed, as images of evacuation and grief spread across the country, there was a sense that something fundamental had shifted. The scale of the violence, carried out in a place long understood as safe, forced a national confrontation with the reality of school shootings. For a moment, it appeared the country might respond with urgency equal to the horror. That expectation faded quickly.