Thursday was not the first time a tax protester went after an Austin IRS building. In 1995, Charles Ray Polk plotted to bomb the IRS Austin Service Center. He was released from prison in October of last year.
The tax protest movement has a long history in the U.S. and was a strong component of anti-government sentiments that surged during the 1990s. Anti-tax protesters typically believe that they do not have to pay income taxes. Some have been convicted in recent years for targeting IRS officials for harassment and even murder.
Officials said they were evaluating an antigovernment manifesto posted on the Internet earlier Thursday, signed "Joe Stack," which suggested he planned the crash. "Violence not only is the answer, it is the only answer," the author wrote toward the end of a tirade against the IRS posted at 9:12 a.m. on a Web site registered to Mr. Stack.
Officials labeled the crash a criminal, not terrorist, attack. "I consider this a criminal act by a lone individual," said Police Chief Art Acevedo.
Still, the North American Aerospace Defense Command launched two F-16 fighter aircraft to patrol the air after the crash. Spokesman Jamie Graybeal called it "a prudent precaution and consistent with our response to recent similar air incidents."
The White House said President Barack Obama was briefed on the plane crash after noon.