Approximately an hour before the crash, Stack allegedly set fire to his $230,000 house located on Dapplegrey Lane in North Austin. He then drove to a hangar he rented at Georgetown Municipal Airport, approximately 20 miles to the north. He boarded his single-engine Piper Dakota airplane and was cleared to take off around 9:45 a.m. Central Standard Time. He indicated to the control tower his flight would be "going southbound, sir." After taking off his final words were "thanks for your help, have a great day."
About ten minutes later his plane descended and collided at full speed into Echelon I, a building containing offices for 190 IRS employees, resulting in a large fireball and explosion.