Cassie Bernall (1981- 20 April 1999) was a student killed in the Columbine High School massacre.
Initial reports suggested that one of the assailants, either Eric Harris or Dylan Klebold, asked Bernall if she believed in God, moments before shooting her dead. She was reported to have answered "yes". This story led to Bernall being hailed as a martyr by some devout Christians of the American Bible Belt. In the months following the tragedy, her mother, Misty Bernall, authored the book She Said Yes: The Unlikely Martyrdom of Cassie Bernall (ISBN 0743400526) which discusses Cassie's teenage life and spirituality.
However the official investigation into the shootings concluded that Cassie did not have the exchange ([1]). Witness Craig Scott, brother of Rachel Scott also killed in the massacre, had originally reported that he had heard Cassie's voice. However when investigators took him back to the scene he indicated that the voice had not come from the area where Bernall had been located. Emily Wyant, who had been sitting with Bernall in the library as the shootings began, confirmed that the exchange had not taken place.
Nevertheless reports that Cassie did say "yes" persist, including for instance on the website ([2]) of the best-selling book.