BREAKING: President Obama Addresses Mass Shooting at Navy Yard in Washington DC

Police say three shooters, including at least one in fatigues, have shot at least 10 people at the Washington Navy Yard.

Police said at least one of the shooters is "down," but it was unclear whether that means the suspect has been arrested or shot. Two remain at large, and police believe they have pinned down one between the third and fourth floors of one of the buildings on the installation in Southeast Washington.

As hundreds of police officers from various agencies converged on the scene, officials at Reagan National Airport ordered all outgoing flights held.

Police on the scene said at least eight civilians were shot, along with the two police officers. One is a D.C. Metro Police officer who was shot two times in the leg and was evacuated on a helicopter that took off from a rooftop, police said. The other officer worked at the base. Except for the officer who was taken away by helicopter, all the other injured were being treated on the ground, police said.