Who Told Giuliani the WTC was Going to Collapse on 9/11?

In the following 9/11 ABC News live interview Giuliani states he was warned of the collapses:

ABC News Broadcast
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“I went down to the scene and we set up headquarters at 75 Barkley Street, which was right there with the Police Commissioner, the Fire Commissioner, the Head of Emergency Management, and we were operating out of there when we were told that the World Trade Center was going to collapse. And it did collapse before we could actually get out of the building, so we were trapped in the building for 10, 15 minutes, and finally found an exit and got out, walked north, and took a lot of people with us.”

When was Giuliani warned?

GIULIANI: The--some of the people that we lost we saw like Father Judge (ph) and Chief Gansy (ph), Bill Fehan (ph), we saw them about 10 minutes before--before we went over to 75 Barkley street. [Washington Post]

Why were only a select few people warned? How many lives would have been saved if everyone had received this warning? Were Port Authority staff told to stay in the buildings? If so, why?

In all, 16 workers waited on the 64th floor and weighed escape options after a hijacked jetliner cut through the skin of the north tower about 30 stories above them. The rest of the floor had cleared out 30 minutes earlier. Why the 16 stayed is open to question. Only McMillan and co-worker Pasquale Buzzelli survived.

Some say the group was instructed to stay by the Port Authority police, even though radio transcripts show the Port Authority's commanding officer at the World Trade Center, Capt. Anthony Whitaker, ordered a full evacuation of the complex a minute before a second hijacked jetliner struck the south tower. On instructions from the Port Authority, McMillan declines to discuss why she stayed. [Bergen Record]

Why were firefighters in the impact zone of WTC 2 unaware that the building was going to collapse? They should have been the ones reporting this information, instead they reported only isolated fires immediately before the building's collapse. Isolated fires do not bring down steel framed buildings.

Have a listen to the radio transmissions of North Brunswick Volunteer Fire/Ladder Company #3 on 9/11. Hear the shock, anguish and suffering as the WTC buildings came to ground. Why didn't these firefighters receive notice that the buildings were going to collapse?

9/11 ABC News report:
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"This is as close as we can get to the base of the World Trade Center. You can see the firemen assembled here, the police officers, FBI agents, and you can see the two towers... a huge explosion now raining debris on all of us."

"We gotta get out of the way!"