On National Television, Rudy Giuliani says he was forewarned of WTC collapse

At 1PM 9/11/01 Eastern Time, Rudy Giuliani told Peter Jennings of ABC News: "[W]e set up headquarters at 75 Barclay Street , and we were operating out of there when we were told that the World Trade Center was gonna collapse. And it did collapse before we could actually get out of the building."

Giuliani's statement that he was told the WTC was going to come down has been seen to imply foreknowledge only by those few individuals who know two things: that there would have been no reason to expect the buildings to come down unless they were known to be rigged with explosives, and that it was Giuliani's own people (in the Office of Emergency Management) who said the buildings were going to come down.

Giuliani said he was warned in advance of the collapse of the South Tower. How and where did he get this warning?