Well, isn't this just the perfect time for this, huh. Capitol is currently on lockdown along with basically everything nearby. If you're here, go away and go somewhere that can actually tell you something, and right now, nobody knows much of anything yet. So be wary of speculation.
EDIT: The gunfire, as info has come in, turned out to come from the Capitol Police, after a woman, a dental hygenist from Stamford, Connecticut, rammed a barrier at the outer perimeter of the White House with her car, with a 1-year-old child on board. Officers gave chase as she sped off, firing on the vehicle, with the chase ending a mile and a half later near the Capitol. The woman, confirmed dead, is suspected of having some sort of mental health problems; she was unarmed. Two Capitol Police officers were hurt: one having been struck by the woman's vehicle, the other after the officer's car struck a barrier. There is no connection to terrorism, so put that thought out of your head.