Dude was just wandering near Capitol Hill with a semi-auto just because:

This video was apparently taken just across from Union Station, which is a few blocks from the Capitol.

From Fox:

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.

The department had sent out an alert that Capitol police was responding to a suspicious package in the Upper Senate Park.

Possible bombs, crazy men with rifles... man, DC should pass a few dozen more gun laws. That'll do it!

More from Capitol Police:

Take a good look, cuz this one is gonna drop out of the news cycle in about 3 seconds!

Add it to the growing list of chaos in DC:

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