A man found parked with an AR-15 near the U.S. Capitol in Washington, D.C., was arrested Tuesday afternoon. 

"USCP Officers just arrested a man with a gun in the park across from Union Station," U.S. Capitol Police wrote on X just before 1 p.m. local time. "At this time we have no reason to believe there is an ongoing threat. We are working to gather more information and will put out more details when they are confirmed." 

Capitol Police confirmed to Fox News that the gun was an AR-15, and the man has been arrested. Authorities believe he was acting alone. 

Police announced road closures along Columbus Circle between Louisiana and Delaware Avenues, NE and D Street between Louisiana and Delaware Avenues, NE due to police activity. 

This is a breaking news story. Check back for updates. Fox News' Alexandra Rago, Chad Pergram and Kelly Phares contributed to this report.