The video seems to have been made in order to highlight the reading class, not the President, so that's why the camera was so far from his face when he first reacted. Obviously the person videotaping did not know what had transpired at the time Andy Card whispered in the President's ear.
For a really good view of the look of horror then steely resolve on the President's face when he heard about the second plane, see if you can find a video of 'The Making of a Wartime President' ( I thinks that's the name of it) done by MSNBC. It shows the classroom visit, the speech just before he left the school, some stills from AF One, the stills from the basement o the WH with Condi, Cheney, etc, the speech in Louisiana, then his arrival at the bunker in the Midwest. Then it goes into the events in the following days. It was actually very well done, without any sort of slaps like the terminally STOOPID Peter Jennings tried to lay on him.