After evacuating the Pentagon due to a pending threat of another attack, the firefighters and other emergency responders return when they receive the all-clear signal.1

Stretcher crews stand ready amongst a crowd of employees at the Pentagon after a hijacked commercial jetliner crashed into the building Sept 11, 2001. Military and civilians of all ranks helped by carrying injured people on stretchers to waiting ambulances. (U.S. Air Force photo by Tech. Sgt. Jim Varhegyi)2

1 Goldberg, A. Papadopoulous, S., et al “Pentagon 9/11” Historical Office, Office of the Secretary of Defense n.d PDF. March 17, 2011 page 159 http://osdhistory.defense.gov/docs/Pentagon%209-11.pdf
2 U.S. Air Force photo by Tech. Sgt. Jim Varhegyi U.S. Air Force Photo Database n.d. Web. April 27, 2011 http://www.af.mil/shared/media/photodb/photos/010911-F-3050V-015.jpg