Capitol Police officers confronted and arrested a man in tan clothes Tuesday who had a gun in the park between Union Station and the Senate side of the campus, the department said.

At 12:39 p.m. 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.

Officers encountered Ahmir Lavon Merrell, 21, of Atlanta, Ga., who was holding the gun down as he walked slowly toward Union Station, the department said.

Chief J. Thomas Manger said officers approached Merrell 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 commended 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,” Manger said.

Manger said it’s unclear why Merrell was on the campus with a gun and that the department is still investigating. He added Merrell “may be dealing with some mental health issues” but “we don’t know that.”

Merrell will be charged with having a firearm on Capitol grounds and other charges are possible, Manger said. Merrell is a registered sex offender, according to the chief.

Manger said the gun “appears to be a semiautomatic weapon” that “looks a little bit like an AR-15.”