Widow of Austin Plane Crash Victim Sues Pilot's Wife

(CNN) -- The widow of an Internal Revenue Service employee killed when a disgruntled taxpayer flew his plane into a seven-story building in Austin, Texas, last week is suing the pilot's wife, according to court documents.

Valerie Hunter, the wife of Vernon Hunter, is accusing Sheryl Stack, wife of Andrew Joseph "Joe" Stack III, of negligence, alleging she she knew or should have known that her husband was a threat to others and, thus, could have prevented the attack, according to the lawsuit filed Monday in Travis County District Court.

"Stack was threatened enough by Joseph Stack that she took her daughter and stayed at a hotel the night before the plane crash. [She] owed a duty to exercise reasonable care to avoid a foreseeable risk of injury to others including [Vernon Hunter]," the suit says.

The lawsuit also seeks to bar the release of Vernon Hunter's autopsy report, saying that, if made public, it would cause Hunter's family to suffer "severe and irreparable emotional distress."

Hunter was killed February 18 when, authorities say, Stack flew his Piper Cherokee PA-28 into a northwest Austin building that housed nearly 200 IRS employees.

Authorities say Stack set fire to his $230,000 home in Austin before embarking on his fatal flight.

Police have said Sheryl Stack spent the previous night in an Austin-area hotel but did not say why. Police said they had received no calls of domestic violence from the house. The only calls to police were made a couple of years ago and concerned barking dogs, officials said said.

A 3,000-word message on a Web site registered to Stack railed against the government, particularly the IRS.

"I saw it written once that the definition of insanity is repeating the same process over and over and expecting the outcome to suddenly be different," the online message said. "I am finally ready to stop this insanity. Well, Mr. Big Brother IRS man, let's try something different; take my pound of flesh and sleep well."

Sheryl Stack issued a statement after the attack expressing "sincere sympathy to the victims and their families."

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."