On April 20, 1999, Kacey Ruegsegger Johnson was a newly transferred junior at Columbine High School. As she sat down to read a magazine in the school library, she had no idea she was about to find herself at the center of an American tragedy, an event that would forever change the course of her life and many others. Moments later, two student gunmen entered the building to continue the massacre they had already begun outside. A now-famous photograph...