Sitting in my cubicle at Ft Hood lurking on FR, finishing my second cup of coffee. My co-worker behind me announced that an aircraft just (accidentally) hit the WTC. I knew then it was no accident. I walked down to our conference room, where several officers and NCOs were gathered watching FNC live on the VTC screen. We watched the second aircraft hit. A seminal moment, we all knew together at that one point in time that we were at war. Several of those guys did not survive in subsequent deployments. Spent the rest of the week working from home since getting on to Fort Hood at that point became a half day exercise in traffic jams, until adequate security arrangements allowed for qucker access.
I remember hearing first reports of the (first) plane being a small, private plane.