Update: As expected, the lockdown has been promptly lifted

LOCKDOWN AT U.S. CAPITOL LIFTED, NBC NEWS REPORTS

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Just hours after the latest mass shooting event in Dallas, one which claimed the most police officer lives since September 11, moments ago the US Capitol was placed under a lockdown possibly due to a gun on the campus. As the Hill reports, Rep. Dennis Ross (R-Fla.) told The Hill that a staffer was seen in the building with a firearm.

Other reports conflict, with AP adding that a "sketchy woman" has been sighted who may have a gun.

One officer outside the Capitol says police are responding to sketchy reports of woman who may have a gun. https://t.co/g8zaJcUY5a — The Associated Press (@AP) July 8, 2016

As Bloomberg adds, Capitol Police are telling staffers to stay inside, lock doors and stay way from external doors and windows. Police haven’t confirmed cause of lockdown; didn’t immediately respond to calls and e-mails seeking further comment. House vote scheduled for 9:15am delayed.

Police in the U.S. say the #Capitol building is on lockdown and authorities are looking for someone — Sky News Newsdesk (@SkyNewsBreak) July 8, 2016

A second lawmaker added the firearm made it past security, where metal detectors and police officers routinely screen anyone coming in to the Capitol or the handful of connected office buildings. Capitol staffers were told to go into an office room and “close, lock and stay away from external doors and windows.”

The latest update from the Capitol Police is the following:

While the building is under lockdown, people are prevented from entering or leaving the Capitol Building and the adjacent visitor’s center.

In a brief statement, the House press gallery told reporters that the chamber met briefly but recessed “immediately.”

Most likely, it is just a case of jittery nerves after yesterday's tragedy, and we expect the all clear to be given shortly.