The U.S. Capitol and all buildings in the Capitol complex were placed on lockdown on Tuesday as authorities investigated a report of "suspicious activity," Capitol police said. The lockdown was later lifted. (Reuters)

The U.S. Capitol and all buildings in the Capitol complex were placed on lockdown on Tuesday as authorities investigated a report of "suspicious activity," Capitol police said. The lockdown was later lifted. (Reuters)

The U.S. Capitol complex was ordered into lockdown Tuesday afternoon after D.C. police chased a car whose passenger shot at officers with a semiautomatic Mac-11 handgun while being pursued through downtown Washington, authorities said.

Three men were arrested, and the weapon — which resembles a machine pistol — was seized, along with ammunition, said D.C. Police Chief Cathy L. Lanier. No officers or bystanders were struck, and police said they did not return fire.

A police spokesman, Dustin Sternbeck, said there was no indication that the Capitol complex was targeted. A statement from the House and Senate sergeant at arms said the lockdown was initiated in part because one of the three men fled. It was lifted after police said he was apprehended near the Waterfront Metro station in Southwest.

Police said the incident began shortly after 4 p.m. two miles from the Capitol at Fourth and P streets SW, near the Southwest Waterfront Park, when police responded to a call about a man with a gun.

Lanier said a car sped away with a man who matched the description provided during the initial call. Police chased the vehicle onto South Capitol Street and into downtown. Just prior to entering the Third Street Tunnel, Lanier said, a passenger reached out a window with the gun and fired at pursuing officers. Lanier said the man then dropped the weapon in the tunnel.

A police sergeant stopped and retrieved the weapon as others continued the pursuit. The car was stopped at the end of the Third Street Tunnel near C Street.

The lockdown was lifted about 4:45 p.m.

Police said the investigation was continuing. They did not identify the suspects, and there was no immediate information on charges.

The incident marked the second time since Friday that the U.S. Capitol complex was placed on lockdown. On July 8, authorities briefly ordered staffers and visitors to shelter in place after police spotted what they thought was a weapon in an employee’s backpack. Authorities said no threat was found.

Karoun Demirjian, Paul Kane, Ed O’Keefe and Clarence Williams contributed to this report.