Two witnesses tell CNN affiliate WJLA they heard their building's fire alarm go off and saw a man with a rifle as they exited the building.
"He aimed the gun and fired our way," Todd Brundidge told the station. "I couldn't believe it."
People frantically tried to escape the building, he said. "They were pushing. They were shoving. People were falling down."
Since Joshua posted earlier this morning, the Washington Post reported that there were three shooters, and now reports the number is two, with one in custody. One of the shooters is believed to have been wearing fatigues. Ten people are reported injured right now with an unknown number killed. Law enforcement are swarming the Navy Yard area, including SWAT teams and ATF. Six schools are on lockdown. The affected area is near the ballpark where the Washington Nationals play.
D.C. Police Chief Cathy Lanier is expected to give a press conference soon with further details.