According to media, FBI has stated that the building hit does not have an FBI office, they do have one in another building nearby. It is now speculation that the pilot intentionally targeted an IRS office that may be in the building hit.
If you Google "austin tx plane crash" you'll turn up a lot of news. If you do it with "joe stack" you'll turn up some very interesting items including an archive of the suicide note that the FBI ordered removed. Lastly, the Billy Eli Band needs a new bassist, check this out. YouTube - Eli Young Band - Lonely All The Time
I read a news story about a year ago regarding the F16's, they are stationed at various locations around the country, that sector is covered by F 16's based at Ellington Field at Houston. They actually have a readiness facility located at the end of the runway so they can be airborne in a couple of minutes. The A/C and crews are rotated every few days from various ANG units in their sector. Our local ANG participates in the rotation schedule.