At 8:46 a.m. on the morning of September 11, 2001, American Airlines Flight 11 struck World Trade Center Tower 1, (The North Tower). Rescorla heard the explosion and saw the tower burning from his office window in the 44th floor of World Trade Center Tower 2 (The South Tower). When a Port Authority announcement came over the P.A. system urging people to stay at their desks, Rescorla ignored the announcement, grabbed his bullhorn, walkie-talkie and cell phone, and began systematically ordering Morgan Stanley employees to evacuate, including the 1,000 employees in WTC 5. He directed people down a stairwell from the 44th floor, continuing to calm employees after the building lurched violently following the crash of United Airlines Flight 175 38 floors above into Tower 2 at 9:03 A.M. Morgan Stanley executive Bill McMahon stated that even a group of 250 people visiting the offices for a stockbroker training class knew what to do because they had been shown the nearest stairway.

Rescorla had boosted morale among his men in Vietnam by singing Cornish songs from his youth, and now he did the same in the stairwell, singing songs like one based on the Welsh song “Men of Harlech”:

“Men of Cornwall stop your dreaming, Can’t you see their spearpoints gleaming?,
See their warriors’ pennants streaming, To this battlefield.
Men of Cornwall stand ye steady, It cannot be ever said ye for the battle were not ready
Stand and never yield!”

Between songs, Rescorla called his wife, telling her, “Stop crying. I have to get these people out safely. If something should happen to me, I want you to know I’ve never been happier. You made my life.” After successfully evacuating most of Morgan Stanley’s 2,687 employees, he went back into the building. When one of his colleagues told him he too had to evacuate the World Trade Center, Rescorla replied, “As soon as I make sure everyone else is out”. He was last seen on the 10th floor, heading upward, shortly before the South Tower collapsed at 9:59 A.M. His remains were never found. Rescorla was declared dead three weeks after the attacks.