Brian Birdwell

At least three Pentagon employees in the area of the building that is hit, and who narrowly survive the attack, initially believe that what they have experienced is a bomb, or bombs, going off:
John Thurman, an Army lieutenant colonel, is in a second floor office just above where the Pentagon is hit. [Washington Post, 4/12/2006] He later describes the moment of impact: “To me it didn’t seem like a plane.… [T]o me it seemed like it was a bomb. Being in the military, I have been around grenade, artillery explosions. It was a two-part explosion to me.… [I]t seemed like that there was a percussion blast that blew me kind of backwards in my cubicle to the side. And then it seemed as if a massive explosion went off at the same time.” He will add: “I had thought that perhaps the terrorists had surreptitiously gotten construction workers to come in and place explosives.” [United States of America v. Zacarias Moussaoui, a/k/a Shaqil, a/k/a Abu Khalid al Sahrawi, Defendant., 4/11/2006 ]
Lt. Nancy McKeown is on the first floor of the Pentagon’s D Ring in the Navy Command Center, which is mostly destroyed when the building is hit. [Washington Post, 1/20/2002; Goldberg et al., 2007, pp. 30-31] She will recall: “[I]t initially felt like an earthquake.… It sounded like a series of explosions going off.… It sounded like a series of bombs exploding, similar to like firecrackers when you light them and you just get a series going off.” [United States of America v. Zacarias Moussaoui, a/k/a Shaqil, a/k/a Abu Khalid al Sahrawi, Defendant., 4/11/2006 ] She yells out to her colleagues, “Bomb!” [Goldberg et al., 2007, pp. 31]
Army Lt. Col. Brian Birdwell is returning to his second floor office, and is just yards from where the building is impacted. [9/11 Commission, 3/31/2003; Dallas Morning News, 9/7/2006] “Bomb! I thought,” he recalls of the moment the building is hit. [US News and World Report, 12/2/2001; Today’s Christian Woman, 7/1/2004]