Ya never know!!
I was in an official gov't building on 9/11 and will tell you I was scared 5hitless. Took better than 6 hours to get home; my mom had been calling my husband all day long to find out if he had heard from me yet; there were all sorts of rumors flying around D.C. and I was stuck on a bus for most of those 6 hours, totally out of contact.
The scariest part (besides not knowing what other buildings in D.C. had been attacked; we on the bus really didn't know that the damage was limited to the Pentagon, since there were rumors of other hits) was driving over a totally deserted Beltway. When we went over that bridge and saw absolutely nothing - the Beltway totally closed down - my jaw dropped and heart started pounding, as was true for everyone on the bus, I'm sure.
After that I always kept a pair of sneakers in my bottom desk drawer. My little talisman against ever being stuck on a bus or not being able to run in heels, if it happened again.