Students calling for an end to gun violence walked out of school Friday, the 19th anniversary of the school shooting in Columbine, Colorado, an event that marked the start of an era of deadly school rampages. The walkouts Friday were sparked by Lane Murdock, a 16-year-old at Ridgefield High School in Connecticut, who began an online petition calling for the protest after the February shooting in Parkland, Florida, that left 14 students and three staff members dead.