Shooting spree at Washington Navy Yard leaves 12 dead

The American flags surrounding the Washington Monument fly at half-staff as ordered by President Barack Obama following the deadly shooting Monday at the Washington Navy Yard, Tuesday, Sept. 17, 2013, in Washington. (AP Photo/J. Scott Applewhite)

This undated cell phone photo provided by Kristi Kinard Suthamtewakul shows a smiling Aaron Alexis in Fort Worth, Texas. The FBI has identified Alexis, 34, as the gunman in the Monday, Sept. 16, 2013 shooting rampage at at the Washington Navy Yard in Washington that left thirteen dead, including himself. (AP Photo/Kristi Kinard Suthamtewakul)

A police cruiser stands guard in front of the Navy Memorial early Tuesday, Sept. 17, 2013 in Washington a day after the fatal shootings at the Navy Yard. Secretary of Defense Chuck Hagel will pay tribute to the victims of the shooting by placing a wreath at the memorial. (AP Photo/J. David Ake

A man who would identify himself only as a Navy Yard employee walks to lay a bouquet of flowers by an anchor outside of the closed Washington Navy Yard in Washington, on Tuesday, Sept. 17, 2013, the day after a gunman launched an attack inside the Washington Navy Yard on Monday, spraying gunfire on office workers in the cafeteria and in the hallways at the heavily secured military installation in the heart of the nation's capital. (AP Photo/Jacquelyn Martin) (AP)

Three women embrace near Nationals Park where family members waited to greet loved ones that were at the Washington Navy Yard, Monday Sept. 16, 2013, in Washington. At least one gunman launched an attack inside the Washington Navy Yard, spraying gunfire on office workers in the cafeteria and in the hallways at the heavily secured military installation in the heart of the nation's capital, authorities said. (AP Photo/Alex Brandon)

September 16, 2013: A police helicopter lifts what appears to be a shooting victim up as it hovers over a rooftop on the Washington Navy Yard campus in Washington. The U.S. Navy said several people were injured and there were multiple fatalities in the shooting at the Navy Yard. (Reuters)

A map detailing the location of a shooting in a naval yard in Washington D.C. (Fox News)

Sept. 16, 2013: A helicopter that has been airlifting people from the top of a building at the Washington Navy Yard circles the area after two gunmen killed several people. (AP Photo/Jacquelyn Martin)

September 16, 2013: A police helicopter is seen as police walk on the roof of a building as they respond to the shooting. (Reuters)

September 16, 2013: Police block off the M Street, SE, as they respond to the shooting. (Reuters)

September 16, 2013: Law enforcement officers respond to the scene of a shooting at the Washington Navy Yard in Washington. (Reuters)

September 16, 2013: Washington Navy Yard personnel are evacuated after a gunman reportedly shot several people inside the base in Washington. (Reuters)

September 16, 2013: A Washington Metropolitan Police officer moves bystanders back from the scene of a shooting at the Washington Navy Yard in Washington. (Reuters)

September 16, 2013: Members of the United States Marine Corps maintain a watch on their barracks as police respond to a shooting at the Washington Navy Yard, in Washington. (Reuters)

September 16, 2013: District of Columbia Mayor Vincent Gray speaks to the press. Earlier, he tweeted, "Please stay clear of Navy Yard area until situation is cleared." (Fox News)

September 16, 2013: DC Metro Police Chief Cathy Lanier updates the press in a mid-day news conference regarding the shooting at the Washington Navy Yard. (Fox News)

September 16, 2013: Navy Yard worker and eyewitness to the shooting, Patricia Ward speaks to the press. (Fox News)

September 16, 2013: U.S. Capitol Police personnel keep watch on the East front of the Capitol as the investigation continues to the shooting at the nearby Washington Navy Yard. (AP)

September 16, 2013: President Barack Obama arrives to speak in the South Court Auditorium on the White House complex in Washington. Before speaking about the economy Obama commented on the Navy Yard shooting. He said the United States is facing "yet another mass shooting" and vowed to hold accountable whoever was responsible. (AP)

September 16, 2013: Evacuees raise their hands as they are escorted from the scene of the shooting. (Reuters)

September 16, 2013: A family member of a Navy Yard worker who was evacuated during a shooting arrives hoping to find him at a makeshift shelter at the Nationals Park baseball stadium near the naval installation in Washington. (Reuters)