http://www.thememoryhole.org/911/bush-911.htm
The only source to describe what happened next is Fighting Back by Bill Sammon. Publishers Weekly described Sammon's book as an "inside account of the Bush administration's reaction to 9-11 [and] a breathless, highly complimentary portrait of the president [showing] the great merit and unwavering moral vision of his inner circle." [Publisher's Weekly, 10/15/02] Sammon's conservative perspective makes his account of Bush's behavior at the end of the photo-op all the more surprising. Bush is described as smiling and chatting with the children "as if he didn't have a care in the world" and "in the most relaxed manner imaginable." White House aide Gordon Johndroe, then came in as he usually does at the end of press conferences, and said, "Thank you, press. If you could step out the door we came in, please." A reporter then asked, "Mr. President, are you aware of the reports of the plane crash in New York? Is there anything...", But Bush interrupted, and no doubt recalling his order, "DON'T SAY ANYTHING YET," Bush responded, "I'll talk about it later." But still the president did not leave. "He stepped forward and shook hands with [classroom teacher] Daniels, slipping his left hand behind her in another photo-op pose. He was taking his good old time. ... Bush lingered until the press was gone." [Fighting Back: The War on Terrorism - From Inside the Bush White House, by Bill Sammon, 10/02, p. 90]
The link has video