WASHINGTON — U.S. Capitol Police used a taser on and arrested a man on Tuesday whom they alleged walked with an assault-style weapon near the Capitol building, though it didn’t initially appear the man made any direct threats against members of Congress.

USCP Chief Tom Manger said during a brief press conference that a 21-year-old registered sex offender from Atlanta, Georgia, will be charged with several federal crimes, including having a firearm on U.S. Capitol grounds.

USCP officers had “limited contact and limited conversations” with Ahmir Lavon Merrell, though Manger said there was “some indication he may be dealing with some mental health issues.”

“We don’t know why he was in the park with a gun. He made no statements as to why he was here, or what he intended to do,” Manger said. “Again, it’s still an ongoing investigation.”

Manger said he didn’t know as of Tuesday afternoon if the gun was loaded.

The U.S. Capitol Police are continuing to investigate the incident to determine where Merrell was before he came into contact with police officers on Tuesday afternoon and whether the semi-automatic firearm that appeared “a little bit like an AR-15” is registered.

U.S. Capitol Police first learned about a man walking with a gun around 12:39 p.m. Eastern when someone saw him in the park between the Capitol building and Union Station, which is about two blocks away. That person told police officers in the Russell Senate Office Building, which sits across the street from the U.S. Capitol and borders the park.

“He was walking along the sidewalk and he was holding the gun down as he walked. They ordered him to stop. He did not,” Manger said. “He was walking at a fairly slow pace down the sidewalk toward Union Station. The officers came up behind him. One officer, who had a taser, tasered him in the back, he fell forward onto his gun. At that point, the officers took him into custody.”

Less than three minutes passed between when the person warned U.S. Capitol Police and when the suspect was detained, Manger said.

The man was walking away from the Capitol and toward Union Station when police officers arrested him, Manger said.

Merrell was taken away from the area in an ambulance around 1:45 p.m. to be checked out by health care providers after the taser was used on him.