A man deliberately flew a private jet into a seven-story office building in Texas yesterday after burning down his house.
he pilot killed himself in the crash and at least two other people were injured, according to police.
Read Stack's suicide note in full
The FBI were last night trying to discover what drove Joseph A Stack, a software engineer, to fly the light aircraft into the Echelon building in north Austin.
The plane, identified by the Federal Aviation Administration as a single-engine Piper Cherokee, took off from the airport in Georgetown, about 40 minutes north of Austin, and was flying under rules that did not require the pilot to maintain contact with air controllers.
The building hit housed offices for the FBI and CIA, but there has been nothing to suggest an intent to target those organisations.
It also listed offices for the Internal Revenue Service (IRS) — the US tax agency.
Officials at the US Department of Homeland Security said it was a “deliberate criminal act” and that Mr Stack was the registered owner of the plane.
Unconfirmed reports suggested that Mr Stack had an ongoing feud with the IRS.
In Washington a federal law enforcement official identified the pilot as Joseph Stack and said investigators were looking at an anti-government message on the internet which was linked to him.
The website outlines problems with the IRS and says violence “is the only answer”.
Homeland security officials said the act was not connected to terrorism, but that US Air Force F-16 Air Force jets had been scrambled “due to an abundance of caution”. Over an hour after impact, flames poured from the smashed windows and thick black smoke filled the air.
Aviation experts expressed shock at the intensity of the flames based on the relatively small amount of fuel the aircraft would have been able to carry, suggesting that Mr Stack may have been carrying some sort of accelerant or explosive on board.
The incident that left the seven-story building in flames renewed fears of domestic terrorism and
gaps in security for private aircraft, although US officials said they had no reason to believe that terrorism was involved.
CNN reported the pilot had set his own house on fire before taking off in the plane and crashing it into the building at about 10am local time. Two people were brought to hospital after the incident, Austin police said.
The fate of the pilot was not immediately clear.
The IRS building, which was engulfed in flames, sits across the street from an FBI office. The IRS said there were about 190 people working in the building and they were trying to account for all their employees.
In Washington, White House spokesman Robert Gibbs said the incident did not appear to be linked to terrorism but he said President Barack Obama was being briefed about it.