Texas Plane Crash: Did Suicidal Pilot Joe Stack Have Explosives on Board?

ABC News- The sheer volume of flames and smoke pouring from the Austin office building where a suicidal pilot slammed his plane at full speed has prompted authorities to investigate whether he had some kind of explosive on board.

Joe Stack, 53, topped off his single engine Piper Cherokee with fuel before crashing into the IRS offices in a kamikaze mission designed to punish the government he believed wronged him.

The full tank of fuel is believed to have contributed to the force of the explosion and subsequent fire, which investigators believe was probably a deliberate tactic by Stack. Investigators are also trying to determine whether Stack had explosives on board with him, sources told ABC News.

Firefighters spent most of the day Thursday trying to extinguish the flames that prevented investigators from recovering Stack's body and searching for anyone else who may have been injured or killed.

Despite the spectacular crash and fire that left the seven story building a blackened hulk, only Stack and one other person are believed to have died. The body of the unidentified victim, a federal employee, was pulled from the building Thursday night.

Investigators believe Stack was the author of a lengthy, hate-filled diatribe that raged against the IRS, President George W. Bush and his own accountant. Posted right around the same time as the 10 a.m. crash, it was signed "Joe Stack (1956-2010.)"

The note was titled "Well Mr. Big Brother IRS Man … take my pound of flesh and sleep well." It details years spent working and paying taxes, but not reaping the benefits of what he considered to be a functional government.

"I choose to not keep looking over my shoulder at 'big brother' while he strips my carcass, I choose not to ignore what is going on all around me, I choose not to pretend that business as usual won't continue; I have just had enough," the note reads.

Records show two of Stack's software companies had been suspended by the state tax board.

"I can only hope that the numbers quickly get too big to be white washed and ignored that the American zombies wake up and revolt; it will take nothing less," he wrote.

Stack's family has not yet commented on the crash, but his wife -- who was mentioned by name in his suicide note -- is expected to speak today.

Forensic psychiatrist Dr. Michael Welner told "Good Morning America" that while it may appear that Stack simply snapped under the weight of tax debt, it was clear from the suicide note that this had been brewing for some time.

"This is the kind of crime that's planned for a long time," Welner said. "I wouldn't be surprised to learn that he practiced."