Around 1:30 p.m. Tuesday, a man walked into the Hart Senate Office Building, approached the security checkpoint and placed a pistol on the X-ray machine.

Officers immediately arrested the man and charged him with one felony and two misdemeanors, all for carrying a gun and ammunition without the proper identification.

But the man, whom Capitol Police declined to identify, did not provide a unique case. Several visitors every year show up on Capitol Hill packing heat — and officers say most are simply unaware that carrying a gun is illegal in D.C. and on the Capitol campus.

“A lot of times people don’t actually realize that a permit is required in the District of Columbia,— Capitol Police spokeswoman Sgt. Kimberly Schneider said. “It does not happen extremely frequently, but it does happen.—

Washington is infamous for having some of the strictest gun laws, even after a Supreme Court ruling last year forced officials to loosen the restrictions. Officers say that can be a shock to visitors from gun-friendly states. In the past year, officers have charged 10 people with carrying a pistol without a license, possessing an unregistered firearm or possessing a firearm as a felon. Some had licenses to carry in other jurisdictions; others had no such excuse.

How many of the cases went to court is unclear, since statistics were not readily available and calls to the U.S. attorney’s office were not returned by press time. But in recent years, prosecutors have dropped at least one high-profile case — that of Phillip Thompson, an aide to Sen. Jim Webb (D-Va.) who was accused in 2007 of bringing a loaded gun into the Russell Senate Office Building.

Various other weapons have also made their way to the Capitol campus — among them, brass knuckles, swords and knives. On the afternoon of Sept. 3, for example, officers arrested a man on the Capitol grounds for carrying a knife and a box cutter in his socks.

Some cases are more serious, others puzzling. In March, for example, 49-year-old Californian Timothy Whitfield asked a Capitol Police officer for directions to the Old Executive Office Building so he could have a meeting with the Joint Chiefs of Staff. Inside his car were three handguns, two rifles, ammunition, a sword, a nightstick, a survival knife and a wooden stick.

“He was further asked if he had any explosives in the vehicle,— the police report reads, “to which he responded he was not a terrorist.—