Washington DC - Capitol Police officers on Tuesday confronted and arrested a man carrying a gun in the park between Union Station and the Senate side of the campus, the department said.

At 12:39 PM ET, a person told Capitol Police officers near the Russell Senate Office Building that there was a man with a gun in the park near Union Station.

A flurry of cop cars and officers descended on the park, causing closures of Columbus Circle and D Street Northeast between Louisiana and Delaware avenues northeast.

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Officers encountered Ahmir Lavon Merrell of Atlanta holding a gun as he walked slowly toward Union Station, the department said.

Chief J. Thomas Manger said officers approached the 21-year-old from behind, ordered him to stop and shouted at him to drop the gun, but Merrell did not comply.

One officer tasered him in the back, causing him to fall forward onto his gun, the department said. He was taken to the hospital. Merrell left a bag in the park, which officers searched.

Manger praised the quick work of the officers: "From the time that the officers got word that there was an individual in the park to the time we had him in custody was about three minutes."

It’s unclear why Merrell was on the campus with a gun and that the department is still investigating. Manger speculated that the man "may be dealing with some mental health issues" but "we don't know that." The type of weapon was described as semiautomatic.

Merrell, who is a registered sec offender, will be charged with having a firearm on Capitol grounds, but other charges are possible.