WASHINGTON — Police arrested a man who steered his tiny, one-person helicopter onto the West Lawn of the U.S. Capitol Wednesday, surprising spring tourists and prompting a temporary lockdown of the Capitol Visitor Center.

Capitol Police didn’t immediately identify the pilot or comment on his motive, but a Florida postal carrier named 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 violent inclinations or intent,” Hughes wrote on his website, thedemocracyclub.org. “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.”

Capitol Police identified the aircraft, which sported the U.S. Postal Service logo and landed about half a city block from the Capitol building, as a “gyro copter with a single occupant.”

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.

The White House said President Barack 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.

John Jewell, 72, a tourist from Statesville, North Carolina, said the craft landed hard and bounced. An officer was already there with a gun drawn. “He didn’t get out until police officers told him to get out. He had his hands up'” and was quickly led away by the police, Jewell said. “They snatched him pretty fast.”

Elizabeth Bevins, a tourist from Atlanta, said she was standing across the street from the Capitol when the little helicopter flew in around 20 or 30 feet high, and it “just sort of plopped down on the lawn.”

Police with rifles yelled at the pilot not to move and told bystanders to run with their heads down, said Nora Neus, 21, a junior at the University of Virginia who was in town for a job interview. “I thought it was a joke at first. My next thought was this is something really bad,” she said.

Downtown Washington is blanketed by restrictions on air traffic that generally prohibit aircraft from flying over the White House, the Capitol, the national Mall and key buildings without special permission.

The situation was under investigation and streets in the area were shut down. Emergency vehicles were dispatched to the area and a robot bomb detector was sent over to the craft.

Amid the commotion, the small craft presented a strange sight sitting on the green lawn of the Capitol, its rotors slowly spinning.