Below is a very short film clip showing President Truman announcing the bombing of Hiroshima and shows the explosion
http://www.bing.com/videos/watch/video/learn-about-the-atomic-bomb-news-footage-from-1945/c86f54c2750bdcdbf833c86f54c2750bdcdbf833-562568037378?q=The+Atom+Bomb&FORM=VIRE3
http://www.bing.com/videos/watch/video/learn-about-the-atomic-bomb-news-footage-from-1945/c86f54c2750bdcdbf833c86f54c2750bdcdbf833-562568037378?q=The+Atom+Bomb&FORM=VIRE3