Aus 9/11 Wiki
Birdwell walked out to the men's room in corridor 4, a move that saved his life. He had just taken three or four steps out of the bathroom when the building was rocked. "Bomb!" the Gulf War vet immediately thought as he was knocked down. When he stood up, he realized he was on fire. "Jesus, I'm coming to see you"
Not only is it a second hand account, but Birdwell was inside the building and did not see the flight of the aircraft.
Source List: Bart