I was at work on the third story of an eight story building when the power went out.  It was an annoying and a “what now” moment.  Then a thick plume of smoke passes by our windows, and it then becomes an “oh sh*t” moment.  Once the panic subsided it was determined that the diesel generator had kicked in.  Of course no one was aware we had one, but we got the knowledge, in a scary kind of way.