DENVER (AP) — The 12 students and one teacher killed in the Columbine High School shooting will be remembered Friday in a vigil on the eve of the 25th anniversary of the tragedy.

The gathering, set up by gun safety and other organizations, is the main public event marking the anniversary, which is more subdued than in previous milestone years.

Former Arizona Congresswoman Gabby Giffords, who began campaigning for gun safety after she was nearly killed in a mass shooting, will be among those speaking at the vigil. So will Nathan Hochhalter, whose sister Anne Marie was paralyzed after she was shot at Columbine. Several months after the shooting, their mother, Carla Hochhalter, took her own life.

The organizers of the vigil, which will also honor all those impacted by the shooting, include Colorado Ceasefire, Brady United Against Gun Violence and Colorado Faith Communities United Against Gun Violence, but they say it will not be a political event.