Federal employees and their unions say an act of domestic terrorism in Texas is the latest worrisome sign of growing anti-government hostility across the country.

Andrew Joseph Stack III, 53, yesterday crashed his small plane into an Austin building housing the IRS and other government agencies, killing himself and one other person. More than 190 IRS employees were in the building at the time, according to an IRS spokesman.

Stack left behind a lengthy note that blamed the federal government for helping the wealthy and hurting ordinary people. And he complained specifically about the IRS, which he said was unresponsive to his complaints.

"Nothing changes unless there is a body count," Stack wrote.

IRS Commissioner Doug Shulman said in a statement that the attack "appears to be an isolated incident." But aggressive behavior against IRS employees are common: The Treasury Department's inspector general for tax administration says it handled more than 1,200 threats and assaults against IRS employees between 2001 and 2008.

And threats against the government in general are becoming more common. The Anti-Defamation League released a report in November that found "a current of anti-government hostility has swept across the United States" since President Obama's inauguration last year. Also, a Homeland Security Department report, disclosed in April, warned of increased potential for right-wing terrorism in the U.S.

"The consequences of a prolonged economic downturn — including real estate foreclosures, unemployment and an inability to obtain credit — could create a fertile environment for right-wing extremists and even result in confrontations between such groups and government authorities similar to those in the past," DHS wrote.

Stack doesn't appear to be a conservative — the end of his letter quotes the Communist Manifesto — but he strikes similar themes of alienation and economic desperation.

He has already attracted a following: People have founded more than two dozen Facebook groups dedicated to Stack since the crash. Some of them attracted more than 200 fans before Facebook deleted them.

On blogs and in e-mails, federal employees said the attack fits into a pattern of escalating anti-government rhetoric. "This won't be the last episode," a Defense Department employee wrote on a forum used by federal employees; "another crazy," said a Federal Aviation Administration staffer. One IRS employee, in an e-mail to Federal Times, blamed the attack on conservative media personalities like Glenn Beck.

Labor unions say they're also concerned: The National Treasury Employees Union, which represents IRS employees, said the attack wasn't an accident and called it a "trauma" for IRS employees. Other unions say they're worried about the potential for future violence.

"We've been concerned about some of the rhetoric that's used to describe federal employees," said Michael Victorian, a spokesman for the American Federation of Government Employees. "We're concerned about the kind of hateful, angry rhetoric that's been used to describe them. … We have been disturbed and very troubled."

The FBI is investigating the crash.