A tape recording of the shooting deaths of four Kent State University students by Ohio National Guardsmen in 1970 reveals the sound of pistol shots 70 seconds earlier, a newspaper reported Friday, citing the work of a forensic audio expert. If the pistol fire is authenticated, it could prove a theory that the Guardsmen thought they were being shot at during a campus Vietnam War protest and also could back up witnesses who said an FBI informant monitoring the protest fired warning shots because he felt threatened. The National Guard opened fire on student protesters on May 4, 1970, killing...