UPDATED 5:10 p.m.
Capitol Police have arrested 41 year-old Paul Agole Ujwok of Virginia and charged him with assault on a police officer.
UPDATED 12:48 p.m.
In a telephone interview with FOX, Phil Morse, Chief of the U.S. Capitol Police said around 11:30 a.m., an officer had just cleared a vehicle into the area between Dirksen and Russell Senate Office Buildings off of Constitution Avenue, NE.
At that point, he says the suspect approached the officer from the crosswalk and was being very "aggressive and threatening" toward the officer. The suspect then lunged toward the officer and the officer tried to contain the suspect.
According to Morse, the suspect then indicated that he may have a gun. The officer took cover, ducking down behind a wall or a barrier and drew his firearm.
A second officer then arrived on the scene and they ordered the suspect to comply with their orders and continued his aggressive and threatening behavior.
Morse said the suspect did not comply with the Police orders leading Capitol Police to stop pedestrian and vehicular traffic on Constitution Avenue and raise the traffic barriers.
The Capitol complex was then locked down, preventing anyone from coming or going.
By that point, a scrum of several officers was on the scene. Morse says a "plainclothes" officer came up behind the suspect and took him down.
Morse says at this point, USCP is not familiar with the suspect and unsure if he works here at the Capitol. The suspect is being interviewed now. No charges have been filed yet and the he hasn't been identified.
The suspect did not have a gun.
Morse says the incident lasted about a minute and the Capitol complex was only locked down for a few minutes.
12:19 p.m. Capitol Police tell FOX that the U.S. Capitol and adjacent office buildings were briefly locked down this morning after a man reportedly approached the Capitol complex with a firearm.
Police say a suspect is custody, but have not released his identity.
During the brief period when no one was allowed to enter or leave any buildings on the campus, activity in the Capitol continued unabated. The House Democratic Caucus continued to meet and action on the floor continued. There was no sign that lawmakers were aware of the security threat outside.
In early 2008, a man with a gun was arrested in Russell Senate Office Building Park. The man had explosives in his car and claimed to be going to see Justice John Roberts.
Then in July of 2009, Capitol Police shot and killed a man in front of the Russell Park Parking Garage after he pulled a gun on them following the high-speed chase down Louisiana Avenue.