Shooting at Navy Yard in Washington

Defense Secretary Chuck Hagel and Joint Chiefs Chairman Gen. Martin Dempsey present a wreath at the Navy Memorial in Washington to remember the victims of Monday's deadly shooting at the Washington Navy Yard, Sept. 17, 2013.

A Navy Yard employee walks to lay a bouquet of flowers by an anchor outside of the Washington Navy Yard, Sept. 17, 2013.

The American flags surrounding the Washington Monument fly at half-staff as ordered by President Barack Obama, one day after the deadly shooting at the Washington Navy Yard, Sept. 17, 2013.

Emergency vehicles and law enforcement personnel respond to a shooting at an entrance to the Washington Navy Yard, Sept. 16, 2013.

Police respond to the shooting at the Washington Navy Yard, Sept. 16, 2013.

U.S. Capitol Police personnel keep watch on the East Plaza of the Capitol as the investigation continues to the shooting at the nearby Washington Navy Yard, Sept. 16, 2013.

Police who responded to shooting at the Washington Navy Yard leave the facility, Sept. 16, 2013.

A Metropolitan Police Department officer walks near the Washington Navy Yard, Sept. 16, 2013.

A police helicopter is seen as police walk on the roof of a building as they respond to a shooting at the Washington Navy Yard, Sept. 16, 2013.

A helicopter lifts a person off the roof as police respond to the report of a shooting at the Navy Yard in Washington, Sept. 16, 2013.

Police work the scene near the Washington Navy Yard, Sept. 16, 2013.

A police vehicle is seen as police respond to a shooting at the Washington Navy Yard, Sept. 16, 2013.

Police work the scene after a gunman was reported at the Washington Navy Yard in Washington, Sept. 16, 2013.