The 12 students and one teacher killed in the Columbine High School shooting will be remembered in a vigil on the eve of the 25th anniversary of the tragedy. Friday's gathering is the main public event marking the anniversary, which is more subdued than in previous milestone years. Among those speaking at the vigil will be former Arizona Congresswoman Gabby Giffords, who began campaigning for gun safety after she was nearly killed in a mass shooting. Organizers say it won't be a political event.
