The man's identity is unknown but the Capitol Police are reportedly searching for the a Chinese translator.
This message was sent out to Senate offices at 6:13 p.m.: "At this time, the Hart Atrium and Seventh floor areas are temporarily closed due to police activity. All Members and staff are to avoid this area until further notice."
Sen. Barack Obama's (D-Ill.) office is on the seventh floor of the Hart Building.
The atrium inside the Hart Building extends up 90 feet.
Update 1 - Ryan Grim reports, as would be expected, a "very heavy" Capitol Police presence inside the Hart Building, where the incident continues to unfold.
Update 2 - Grim said the man appears t o be middle aged, and he is standing outside the railing on the seventh floor. He is moving around slightly but otherwise appears calm. He is talking to Capitol Police but it is unclear whether a translator has been found or whether the police are able to effectively communicate with him.
Update 3 - A translator has been found and is talking to the man now.
Update 4 - Capitol Police have now removed all reporters from the Hart Building, saying the Senate has adjourned and the buiding is officially closed. A press conference is scheduled shortly.