Questions are swirling about how a postal worker from Florida managed to land a small gyrocopter Wednesday on the West Lawn of the U.S. Capitol without being shot out of the sky by authorities.

Mailman Doug Hughes took responsibility for the stunt on a website where he said he was delivering letters to all 535 members of Congress in order to draw attention to campaign finance corruption.

“As I have informed the authorities, I have no violence inclinations or intent,” Hughes wrote on his website, the “An ultralight aircraft poses no major physical threat -- it may present a political threat to graft. I hope so. There's no need to worry -- I'm just delivering the mail."

House Homeland Security panel Chairman Michael McCaul, R-Texas, said the pilot landed on his own, but that had he made it much closer to the Capitol authorities were prepared to shoot him down.

"Had it gotten any closer to the speaker's balcony they have long guns to take it down, but it didn't. It landed right in front," McCaul said.

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Secret Service spokesman Brian Leary said Wednesday night that media reports earlier in the day claiming the Secret Service Tampa Field Office had been alerted to the flight in advance were not true.

"The subject involved in today's incident had come to the attention of the USSS approximately one and a half years ago," Leary said. "On October 4, 2013, the Secret Service obtained information from a concerned citizen about an individual purporting their desire to land a single manned aircraft on the grounds of the United States Capitol or the White House." He added a complete investigation was conducted at the time.

The Federal Aviation Administration said the pilot had not been in contact with air traffic controllers and the FAA didn't authorize him to enter restricted airspace.

Airspace security rules that cover the Capitol and the District of Columbia prohibit private aircraft flights without prior coordination and permission. Violators can face civil and criminal penalties.

A law enforcement official told Fox News Wednesday night that the pilot has not yet been formally charged. The U.S. Attorney’s Office for the District of Columbia is currently reviewing the incident for possible charges.

The White House said President Obama had been briefed on the situation.

Witnesses said the craft approached the Capitol from the west, flying low over the National Mall and the Capitol reflecting pool across the street from the building. It barely cleared a row of trees and a statue of Gen. Ulysses Grant. The gyrocopter landed hard and bounced and the pilot was quickly arrested.

The open-air aircraft sported a U.S. Postal Service logo.

One witness told The Associated Press that when the aircraft landed, police with rifles yelled at the pilot not to move, and told bystanders to run, with their heads down.

About two hours after the landing, police said a bomb squad had cleared the aircraft, and that authorities would be moving it to a secure location.

The incident once again thrusts Washington’s airspace into the spotlight. In January,a quadcopter drone crashed onto the White House grounds, sparking calls for tighter security.

A gyrocopter resembles a small helicopter. However, unlike a helicopter, a gyrocopter’s blades are not powered, with the aircraft relying instead on an engine-powered propeller to provide thrust. Often used as recreational aircraft, gyrocopters have also been deployed in law enforcement.

Fox News' Chad Pergram and The Associated Press contributed to this report.