From an old and dear who works near the building that got hit:
'Not too close, but a little close for comfort! Not the FBI office, as earlier reported, but bldg next to it. My friend Patrick's cousin said he saw the plane flying very low and then suddenly bank into the bldg.'
And that's all I know, except what's on the TV. This story from local Austin TV station.
Later: Ahhh, now we got a likely perpetrator. Here's his catalogue of grievances. Mad as hell and wasn't going to take it any more. Apparently aiming for the IRS office.