DCist:

Police are now speaking with the man inside the building, but are not confirming much less, other than he is an Asian male, his concerns are with Discovery and that it is possible that he has a bomb. WTOP’s Adam Tuss reports that most employees have been evacuated. WUSA9 has now tweeted that their report that their report of the gunman’s demands have not been confirmed.

The demands referenced are the manifesto that was apparently first posted in 2008.