Lt. Col. Ted Anderson : "We ran to the end of our building, turned left and saw nothing but huge, billowing black smoke, and a brilliant, brilliant explosion of fire." (...) One of the Pentagon's two fire trucks was parked only 50 feet from the crash site, and it was "totally engulfed in flames," Anderson says.
Nearby, tanks full of propane and aviation fuel had begun igniting, and they soon began exploding, one by one. (...) Back in the building again, Anderson said he began "screaming and hollering for people as secondary and third-order explosions started going off. One of them was a fire department car exploding-I think my right eardrum exploded at the same time, and it unequivocally scared the heck out of me."
http://www.msnbc.com/news/635293.asp---------
One of the aircraft's engines somehow ricocheted out of the building and arched into the Pentagon's mall parking area between the main building and the new loading dock facility, said Charles H. Krohn, the Army's deputy chief of public affairs. Those fleeing the building heard a loud secondary explosion about 10 min. after the initial impact.
http://www.aviationnow.com/content/publication/awst/20010917/aw48.htm
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Angkor, I was replying to your earlier post. I am sure there were many rumors going around. I was just reporting what I heard from a first person source. She was talking to her husband at the Pentagon when an explosion happened. She was almost knocked over by it. He was at the Pentagon and wasn't hearing it except over the telephone. Maybe he was in a bunker.