Giuliani was in school on the morning of Sept. 11, 2001, when he heard about two airliners crashing into the Twin Towers of the World Trade Center.

“It was an extremely sad day for anybody,” he said. “It’s still a day I think about. I couldn’t believe what I was hearing. It was shocking, obviously, extremely devastating.

“I had just that morning seen the towers. It was a beautiful September morning ... still felt like summertime, as beautiful as you can imagine. An hour before I’d seen them standing tall like they always had, and what happened afterwards obviously was incredible disheartening.”

A third hijacked plane crashed into the Pentagon outside of Washington, D.C., and a fourth plane, after some passengers and flight crew members attempted to regain control, crashed in rural Pennsylvania. A total of 2,974 victims and 19 hijackers died in the attacks.”

In the aftermath, Giuliani witnessed the outpouring of patriotism.

“New Yorkers showed their spirit that day,” he said. “It was not limited to New Yorkers ... Americans showed their spirit that day. I saw firefighters at Ground Zero from Kansas City, from California, even from Europe. It was incredible seeing people understand what was going on and want to lend a helping hand.”