WASHINGTON (AP) – An armed man crashed his vehicle into a security barricade at the Capitol on Monday, ran into the building and was arrested, forcing the complex to briefly be locked down, authorities said.

The man was armed with a gun, said one security officer speaking anonymously pending an official briefing. The officer said the man was captured by police after running through the Rotunda in the center of the Capitol and down a stairway into the basement. He said the man appeared to be having a seizure, and was taken to a hospital.

A congressional aide said the man appeared to be carrying a small weapon and that an ambulance had been called because of the apparent seizure. The aide said that police were reviewing a videotape of the incident and were expected to release a statement soon.

Police shut down the complex as they investigated the incident, and to ensure that all people there were authorized to be there. The incident happened shortly before 8 a.m., EDT, witnesses said. The Capitol complex was reopened within the hour.

Eric Ueland, chief of staff for Senate Majority Leader Bill Frist, said that after the capture, police conducted a search through the Capitol to ensure there had been no other penetration.

Construction workers and police said the man drove his SUV through a barricade at the Capitol, where a major visitors’ center is under construction. His vehicle also crashed into a water fountain on the plaza in the middle of the construction area.

Witnesses said the man, wearing a blue ballcap, ran into the Capitol near the Rotunda and was pursued by police.

In the summer of 1998, two Capitol Police officers were shot to death when a man with a history of mental illness opened fire in the building. The man was wounded and captured.

Police cordoned off the vehicle, a light-colored SUV, which sustained a damaged front fender, and were searching it.