NEW : Seats removed from plane , fuel drum missing from airport . IRS takes lead role in investigation into Texas , Austin , crash . Pilot 's wife expresses her `` sincere sympathy to the victims and their families '' A 3,000-word message on a Web site registered to Stack railed against the government , particularly the IRS . Art Acevedo believed to have flown plane into FBI building in suicidal attack .
NEW : Seats removed from plane , fuel drum missing from airport . IRS takes lead role in investigation into Texas , Austin , crash . Pilot 's wife expresses her `` sincere sympathy to the victims and their families '' Art Acevedo believed to have flown plane into FBI building in suicidal attack .