Andy Cross, The Denver Post

Tom Mauser, father of Daniel Mauser who was killed in the Columbine High School shooting, gets the crowd fired up at Civic Center Park for the March for Our Lives rally March 24, 2018. The student-led rally and march is one of more than 400 sister demonstrations taking place across the country March 24 in partnership with the Washington DC march that is organized by the student survivors of the Feb. 14 shooting in Parkland, Florida.