was an atomic blast from tinker air force base. >> i was trying to make sense out of it. i did not think it was a bomb. >> they have dog teams here searching for survivors and for bodies. >> scores of people have been killed outright and hundreds more injured. the blast radius encompasses a 16-block area, but the murrah building is ground zero. ♪ >> bureau of alcohol, tobacco and firearms was headquartered there. some of its members are missing. >> social security was located there, a child care center was located there. initial estimates coming in