A STAFF member carrying a gun entered the US Capitol on Thursday and was later arrested, police said. 

An alert went out to Capitol complex staff in the Longworth building around 7:50am about "a security threat inside the building" and warning occupants to "move inside your office or the nearest office." Minutes later, the US Capitol Police said the threat was cleared.

Jeffrey Allsbrooks, 57, a staff member with the House Chief Administrative Office, USCP said in a statement, was "tracked down four minutes later" after officers "spotted the image of a handgun in a bag on the x-ray screen."

Allsbrooks told officers he forgot the gun was in the bag.

The USCP is charging him with carrying a pistol without a license, and said the case remains under investigation to look "into what happened before, during and after those four minutes."

The security alert came just hours before President Joe Biden was scheduled to arrive at the Capitol for a ceremony honoring the late Sen. Bob Dole (below), R-Kans., who is lying in state in the Capitol Rotunda. 

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The incident also comes at the end of a year that saw several threats and violent incidents at the Capitol. In January, a mob of pro-Trump supporters swarmed the Capitol in an attempt to stop the counting of electoral ballots that affirmed Joe Biden had won the presidency. Several people died.

Months later, a man rammed a car into a security barrier near the Capitol, killing an USCP officer. There have also been several bomb threats.