Stack was believed to have a grudge against the Internal Revenue Service, who had offices in the building. Stack allegedly set fire to his home and then flew his single-engine Piper airplane into the seven-story office building on the morning of Feb. 18.
The crash killed two people, including Stack and IRS worker Vernon Hunter, and ultimately damaged the building to such a degree that it had to be completely gutted and rebuilt -- a process that is ongoing.
After the attack, Stack's adult daughter, Samantha Bell, told ABC's "Good Morning America" the plane attack was "inappropriate," but she still praised his anti-government and anti-tax views.
She said her father was not a hero for taking a life, but rather because of his actions "maybe people will listen."
The NTSB's report is below:
On February 18, 2010, approximately 0958 Central Standard Time, N2889D, a Piper PA-28-236 single-engine airplane, was destroyed after the pilot intentionally flew it into the side of an office building in Austin, Texas. The private pilot and an employee who worked in the building were killed. The airplane was registered to and operated by the pilot. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight conducted under 14 Code of Federal Regulations Part 91. The flight originated from the Georgetown Municipal Airport (GTU), Georgetown, Texas, at 0944.
Preliminary review of air traffic control communications and radar data revealed that after the pilot was cleared for take off from Georgetown Airport, he proceeded southbound and climbed to an altitude of 4,800 feet. During this time, a controller approved a radio frequency change and the pilot responded, "Eight niner delta thanks for your help have a great day." No further communications were made with the pilot. At 0954, the airplane was observed on radar descending out of 4,800 feet and making a turn toward the west. At 0957, the airplane was last observed on radar at an altitude of 1,000 feet on a southwesterly heading before the data ended.
The airplane collided with the office building between the first and second floors, and exploded on impact. The airplane's engine, two (of three) propeller blades, and the right wing came to rest outside of the building. The empennage came to rest on the ledge of the building and was partially hanging over the edge. The left wing, portions of the fuselage, and a propeller blade, were found inside the building on the second floor. The flaps were found in the fully retracted position. The airplane was destroyed by impact and the post-impact fire.
The weather at Austin Bergstrom International Airport (AUS), Austin Texas, at 0953, was reported as calm wind, visibility 10 miles, few clouds at 25,000 feet, temperature 9 degrees Celsius, dew point 1 degree Celsius, and a barometric pressure setting of 30.24.
As this event was an intentional act, the FBI has assumed jurisdiction and control of the investigation.