12 years ago I was at work, annoyed that a meeting I had spent a lot of time preparing for had been cancelled at the last minute. I heard that a plane had flown into the World trade Center, and I was thinking of some unlucky Cessna pilot who had that misfortune as a similar occurrence had happened recently. So I was thinking it was no big deal. A little later when I saw the images on a TV someone had set up in a conference room, I knew this was something totally different.
About that time Julayne started sending me text messages of what she was seeing on TV. It was chilling to be quasi-working, and get a text that first tower fell and then the second one. (Months later it still gave me chills to review the text messages of that day. I held onto them until I finally changed phones.)
Hours later, after the towers had fallen and the FAA was frantically landing airplanes, a co-worker and I had to go visit a prospective client. Rumors were spreading that a plane was heading for the Ren Cen in downtown Detroit. Being outside felt kinda dangerous, but sitting in the client's office felt extremely surreal. As we're making our pitch, I just wanted to get out of there and get home (and the guy never did hire us).
All in all, a day I will never forget.