This booking photo provided by the Fort Worth Police Department shows Aaron Alexis, arrested in September, 2010, on suspicion of discharging a firearm in the city limits. 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. Uncredited, Associated Press

This booking photo provided by the Fort Worth Police Department shows Aaron Alexis, arrested in September, 2010, on suspicion of discharging a firearm in the city limits. 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. Uncredited, Associated Press

A flag flies at half-staff above the White House after President Barack Obama made the proclamation to honor the victims of the shootings at the Washington Navy Yard on 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. Evan Vucci, Associated Press

A member of the Navy has her ID checked as only essential personnel are allowed in to a 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. Jacquelyn Martin, Associated Press

This photo provided by NASA show a United States flag is flown at half-staff just outside the Mid-Atlantic Regional Spaceport (MARS) Pad-0A with the Orbital Sciences Corporation Antares rocket, Tuesday, Sept. 17, 2013 at Wallops Island, Va. President Barack Obama directed that flags be lowered to half-staff to pay tribute to the victims of the Washington Navy Yard shootings. NASA's commercial space partner, Orbital Sciences Corporation, is targeting a Sept. 18 launch of the Cygnus cargo spacecraft, demonstration cargo resupply mission, to the International Space Station. NASA, Bill Ingalls, AP PHoto

Essential personnel are allowed into a 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. Jacquelyn Martin, Associated Press

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. Jacquelyn Martin, Associated Press

A police officer stands by a locked gate at the Washington Navy Yard, closed except to essential personnel, 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. The gate at right is open to allow ID checks of essential personnel. Jacquelyn Martin, Associated Press

An officer who said he was with the Department of Defense, right, and members of the Navy, stand guard inside the gate 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. Jacquelyn Martin, Associated Press

A flag flies at half-staff above the White House after President Barack Obama made the proclamation to honor the victims of the shootings at the Washington Navy Yard on 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. Evan Vucci, Associated Press

Staff of the Naval Sea Systems Command headquarters walk away from Nationals Park after being bused there from the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. 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. Jacquelyn Martin, Associated Press

A woman gestures on the phone as staff of the Naval Sea Systems Command headquarters arrive at Nationals Park after bused from the Washington Navy Yard, in Washington, Monday, Sept. 16, 2013. 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. Jacquelyn Martin, Associated Press

Family and friends wait to greet staff of the Naval Sea Systems Command headquarters as they are bused from the Washington Navy Yard to Nationals Park, in Washington, Monday, Sept. 16, 2013. 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. Jacquelyn Martin, Associated Press

Family and friends rush to greet staff of the Naval Sea Systems Command headquarters after they were bused from the Washington Navy Yard to Nationals Park, in Washington, Monday, Sept. 16, 2013. 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. Jacquelyn Martin, Associated Press

Family and friends greet staff of the Naval Sea Systems Command headquarters after they were bused from the Washington Navy Yard to Nationals Park, in Washington, Monday, Sept. 16, 2013. 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. Jacquelyn Martin, Associated Press

Staff of the Naval Sea Systems Command headquarters exchange a salute while being greeted by family and friends as they are bused from the Washington Navy Yard to Nationals Park, in Washington, Monday, Sept. 16, 2013. 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. Jacquelyn Martin, Associated Press

Family and friends wait to greet staff of the Naval Sea Systems Command headquarters as they are bused from the Washington Navy Yard to Nationals Park, in Washington, Monday, Sept. 16, 2013. 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. Jacquelyn Martin, Associated Press

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. Kristi Kinard Suthamtewakul, Associated Press

Family and friends wait to greet staff of the Naval Sea Systems Command headquarters, as they are bused from the Washington Navy Yard to Nationals Park, in Washington, Monday, Sept. 16, 2013. 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. Jacquelyn Martin, Associated Press

Secretary of the Navy Ray Mabus and Washington Hospital Center chief operating officer Janis M. Orlowski walk to a news conference in Washington, Monday, Sept. 16, 2013, after visiting the people injured in the shooting at Washington Navy Yard. Jose Luis Magana, Associated Press

Restaurant owner Oui Suthamtewakul, right, and Micheal Ritrovato speak about working with Aaron Alexis , who was once employed by Suthamtewakul, Monday, Sept. 16, 2013, in Fort Worth, Texas. Police have identified Alexis as the gunman in Monday's shooting rampage at at the Washington Navy Yard in Washington. Mayor Vincent Gray said at a news conference Monday afternoon that Alexis was among the dead. LM Otero, Associated Press

Debris sits in front of the last known address of Aaron Alexis Monday, Sept. 16, 2013, in Fort Worth, Texas. Police have identified Alexis as the gunman in Monday's shooting rampage at at the Washington Navy Yard in Washington. Mayor Vincent Gray said at a news conference Monday afternoon that Alexis was among the dead. LM Otero, Associated Press

A reporter knocks on the door of the last known address of Aaron Alexis Monday, Sept. 16, 2013, in Fort Worth, Texas. Police have identified Alexis as the gunman in Monday's shooting rampage at at the Washington Navy Yard in Washington. Mayor Vincent Gray said at a news conference Monday afternoon that Alexis was among the dead. LM Otero, Associated Press

Secretary of the Navy Ray Mabus walks out of the Washington Hospital Center, where several of the victims from the attack at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. 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. Jose Luis Magana, Associated Press

Secretary of the Navy Ray Mabus walks with Dr. Janis M. Orlowski at Washington Hospital Center, in Washington, on Monday, Sept. 16, 2013, after Mabus visited people injured in the shooting at the Washinton Navy Yard. With them Ad. Jonathan Greenert, center. Jose Luis Magana, Associated Press

A police officer gives instructions to people coming out of the main gate of the Washington Navy Yard facility who were trapped inside during a lock down when at least one gunman launched an attack inside a building at the Navy Yard, Monday, Sept. 16, 2013. Manuel Balce Ceneta, Associated Press

Secretary of the Navy Ray Mabus speaks with reporters as he leaves the Washington Hospital Center, in Washington, on Monday, Sept. 16, 2013, after visiting people injured at the shooting at Washington Navy Yard. 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. Jose Luis Magana, Associated Press

Police keep streets clear from cars and pedestrians after a gunman was reported at the Washington Navy Yard in Washington, on Monday, Sept. 16, 2013. 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. Jacquelyn Martin, Associated Press

A Metropolitan Police Department officer walks near the Washington Navy Yard after 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, in Washington, on Monday, Sept. 16, 2013. Jacquelyn Martin, Associated Press

U.S. Capitol Police officers stand guard as doors are locked down inside the Capitol Building during the shooting at the Washington Navy Yard, Monday, Sept. 16, 2013, in Washington. J. Scott Applewhite, Associated Press

U.S. Capitol Police officers stand guard as doors are locked down inside the Capitol Building during the shooting at the Washington Navy Yard, Monday, Sept. 16, 2013, in Washington. J. Scott Applewhite, Associated Press

Members of the military guard a military garage near the Washington Navy Yard where a gunman was reported in Washington, on Monday, Sept. 16, 2013. The exact number of people killed and the conditions of those wounded was not immediately known. Jacquelyn Martin, Associated Press

A U.S. Park Police helicopter continues a search pattern above the scene of a shooting at the Washington Navy Yard on Monday, Sept. 16, 2013 in Washington. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning, and officials said several people were killed and more were wounded, including a law enforcement officer. Evan Vucci, Associated Press

Police boats and a U.S. Park Police helicopter are seen on the scene of a shooting at the Washington Navy Yard on Monday, Sept. 16, 2013 in Washington. At least one gunman opened fire inside a building at the Washington Navy Yard and officials said several people were killed and wounded. Evan Vucci, Associated Press

Law enforcement personnel are seen outside the gate into the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning, and officials said several people were killed and more were wounded, including a law enforcement officer. Susan Walsh, Associated Press

President Barack Obama pauses as he speaks in the South Court Auditorium on the White House complex, Monday, Sept. 16, 2013, in Washington. Before speaking about the economy Obama spoke on the shooting at the Washington Navy Yard, mourning what he called "yet another mass shooting" in the United States that he says took the life of American patriots. Pablo Martinez Monsivais, Associated Press

President Barack Obama arrives to speak in the South Court Auditorium on the White House complex, Monday, Sept. 16, 2013, in Washington. Before speaking about the economy Obama spoke on the shooting at the Washington Navy Yard, mourning what he called "yet another mass shooting" in the United States that he says took the life of American patriots. Carolyn Kaster, Associated Press

President Barack Obama walks out before speaking in the South Court Auditorium on the White House complex, Monday, Sept. 16, 2013, in Washington. Before speaking about the economy Obama commented on the Washington Navy Yard shooting. Pablo Martinez Monsivais, Associated Press

President Barack Obama pauses as he speaks about the shooting at the Washington Navy Yard during a event on the economy in the South Court Auditorium on the White House complex, Monday, Sept. 16, 2013, in Washington. Carolyn Kaster, Associated Press

President Barack Obama speaks in the South Court Auditorium on the White House complex, Monday, Sept. 16, 2013, in Washington, about the Washington Navy Yard shooting. Pablo Martinez Monsivais, Associated Press

President Barack Obama arrives to speak in the South Court Auditorium on the White House complex, Monday, Sept. 16, 2013, in Washington. Before speaking about the economy Obama commented on the Washington Navy Yard shooting. Carolyn Kaster, Associated Press

President Barack Obama pauses as he speaks in the South Court Auditorium on the White House complex, Monday, Sept. 16, 2013, in Washington. Before speaking about the economy Obama commented on the Washington Navy Yard shooting. Carolyn Kaster, Associated Press

President Barack Obama speaks in the South Court Auditorium on the White House complex, Monday, Sept. 16, 2013, in Washington. Before speaking about the economy Obama commented on the Washington Navy Yard shooting. Carolyn Kaster, Associated Press

Law enforcement personnel gather outside the gate of the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. Susan Walsh, Associated Press

People hold their hands to their heads as they are escorted out of the building where a gunman was reported at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. Jacquelyn Martin, Associated Press

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 Monday, Sept. 16, 2013, in Washington. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. J. Scott Applewhite, Associated Press

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 Monday, Sept. 16, 2013, in Washington. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. J. Scott Applewhite, Associated Press

A U.S. Park Police helicopter flies over a building at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. President Barack Obama is mourning what he called "yet another mass shooting" in the United States that he says took the life of American patriots. Susan Walsh, Associated Press

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 Monday, Sept. 16, 2013, in Washington. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. J. Scott Applewhite, Associated Press

President Barack Obama arrives to speak in the South Court Auditorium on the White House complex, Monday, Sept. 16, 2013, in Washington. Before speaking about the economy Obama commented on the Navy Yard shooting. Carolyn Kaster, Associated Press

Dr. Janis M. Orlowski, chief operating officer at Washington Hospital Center speaks at a news conference in Washington, Monday, Sept. 16, 2013, about the conditions of the people who were brought to the hospital from the shooting at the Washington Navy Yard building. Orlowski said the hospital was treating three gunshot victims in critical condition. One was Washington, D.C., metropolitan police officer and two were civilian women. Jose Luis Magana, Associated Press

Dr. Janis M. Orlowski, chief operating officer at Washington Hospital Center speaks at a news conference in Washington, Monday, Sept. 16, 2013, about the conditions of the people who were brought to the hospital from the shooting at the Washington Navy Yard building. Orlowski said the hospital was treating three gunshot victims in critical condition. One was Washington, D.C., metropolitan police officer and two were civilian women. Jose Luis Magana, Associated Press

A police boat and helicopter patrol near the scene of a shooting at the Washington Navy Yard on Monday, Sept. 16, 2013, in Washington. At least one gunman opened fire inside a building at the Washington Navy Yard, and officials said six people were killed and as many as 10 were wounded, including a law enforcement officer. Evan Vucci, Associated Press

Security personnel respond near the Washington Navy Yard where a gunman was reported in Washington, on Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning, and officials said six people were killed and as many as 10 were wounded, including a law enforcement officer. Manuel Balce Ceneta, Associated Press

Dr. Janis M. Orlowski, chief operating officer at Washington Hospital Center speaks at a news conference in Washington, Monday, Sept. 16, 2013, about the conditions of the people who were brought to the hospital from the shooting at the Washington Navy Yard building. Orlowski said the hospital was treating three gunshot victims in critical condition. One was Washington, D.C., metropolitan police officer and two were civilian women. Jose Luis Magana, Associated Press

A man is airlifted from the top of a building inside the Washington Navy Yard after a gunman was reported at the Navy Yard in Washington, on Monday, Sept. 16, 2013. The exact number of people killed and the conditions of those wounded was not immediately known. About 3,000 people work at the Naval Sea Systems Command headquarters. Jacquelyn Martin, Associated Press

A helicopter that has been airlifting people from the top of a building at the Washington Navy Yard circles the area after a gunman was reported at the Washington Navy Yard in Washington, on Monday, Sept. 16, 2013. The exact number of people killed and the conditions of those wounded was not immediately known. About 3,000 people work at the Naval Sea Systems Command headquarters. Jacquelyn Martin, Associated Press

Police bring in equipment by an anchor outside of an entrance to the Washington Navy Yard where a gunman was reported in Washington, on Monday, Sept. 16, 2013. The exact number of people killed and the conditions of those wounded was not immediately known. About 3,000 people work at the Naval Sea Systems Command headquarters. Jacquelyn Martin, Associated Press

The main street near the Washington Navy Yard is crowded with official vehicles following a shooting at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning (AP Photo/Susan Walsh) Susan Walsh, AP

A police boat patrols near the scene of a shooting at the Washington Navy Yard on Monday, Sept. 16, 2013, in Washington. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. (AP Photo/ Evan Vucci) Evan Vucci, ASSOCIATED PRESS

Police work the scene on M Street, SE in Washington, where a gunman was reported at the Washington Navy Yard in Washington, on Monday, Sept. 16, 2013. The U.S. Navy says one person is injured after a shooting at a Navy building in Washington. Jacquelyn Martin, Associated Press

Police work the scene on M Street, SE in Washington near the Washington Navy Yard on Monday, Sept. 16, 2013. The U.S. Navy says one person is injured after a shooting at a Navy building in Washington. Police and emergency crews gathered Monday morning outside the Naval Sea Systems Command Headquarters building, where the shooting was reported. Jacquelyn Martin, Associated Press

A U.S. Park Police helicopter removes a man in a basket from the Washington Navy Yard Monday, Sept. 16, 2013. Earlier in the day, the U.S. Navy said it was searching for an active shooter at the Naval Sea Systems Command headquarters, where about 3,000 people work. The exact number of people killed and the conditions of those wounded was not immediately known. Jacquelyn Martin, Associated Press

A U.S. Park Police helicopter removes a man in a basket from the Washington Navy Yard Monday, Sept. 16, 2013. Earlier in the day, the U.S. Navy said it was searching for an active shooter at the Naval Sea Systems Command headquarters, where about 3,000 people work. The exact number of people killed and the conditions of those wounded was not immediately known. Jacquelyn Martin, Associated Press

A U.S. Park Police helicopter removes a man in a basket from the Washington Navy Yard Monday, Sept. 16, 2013. Earlier in the day, the U.S. Navy said it was searching for an active shooter at the Naval Sea Systems Command headquarters, where about 3,000 people work. The exact number of people killed and the conditions of those wounded was not immediately known. Jacquelyn Martin, Associated Press

Police work the scene on M Street S.E. in Washington, where a gunman was reported in a military building at the Washington Navy Yard Monday, Sept. 16, 2013. Shots have been fired and employees directed to a shelter. Police and federal agents from multiple law enforcement agencies responded to the scene and streets in the area were closed. Jacquelyn Martin, Associated Press

A U.S. Park Police helicopter with a person in the rescue basket, flies over a building at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. (AP Photo/Susan Walsh) Susan Walsh, ASSOCIATED PRESS

A U.S. Park Police helicopter flies over a building at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning, (AP Photo/Susan Walsh) Susan Walsh, ASSOCIATED PRESS

District of Columbia Police Chief Cathy Lanier briefs reporters on the shooting at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013, where at least one gunman opened fire inside a building at the Washington Navy Yard. (AP Photo/Susan Walsh) Susan Walsh, AP

An officer stands near the gate of the Washington Navy Yard in Washington, Monday, Sept. 16, 2013, after a gunman opened fire. (AP Photo/Susan Walsh) Susan Walsh, AP

People hold their hands to their heads as they are escorted out of the building where a gunman was reported at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. (AP Photo/Jacquelyn Martin) Jacquelyn Martin, ASSOCIATED PRESS

Law enforcement personnel gather outside the gate of the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. (AP Photo/Susan Walsh) Susan Walsh, AP

U.S. Capitol Police personnel keep watch at the Constitution Avenue entrance to the East Plaza of the Capitol as the investigation continues at the nearby high-security Washington Navy Yard where a gunman went on a shooting rampage, Monday, Sept. 16, 2013, in Washington. (AP Photo/J. Scott Applewhite) J. Scott Applewhite, AP

District of Columbia Police Chief Cathy Lanier briefs reporters on the shooting at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. Standing to the right of Lanier is District of Columbia Mayor Vincent Gray. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning (AP Photo/Susan Walsh) Susan Walsh, ASSOCIATED PRESS

District of Columbia Mayor Vincent Gray briefs reporters on the shooting at the Washington Navy Yard in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning. (AP Photo/Susan Walsh) Susan Walsh, ASSOCIATED PRESS

A U.S. Capitol Police armored vehicle patrols the East Plaza of the Capitol in front of the Senate as the investigation continues at the nearby high-security Washington Navy Yard where gunmen went on a shooting rampage, Monday, Sept. 16, 2013, in Washington. (AP Photo/J. Scott Applewhite) J. Scott Applewhite, AP

Security personnel respond near the Washington Navy Yard where a gunman was reported in Washington, on Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning, and officials said six people were killed and as many as 10 were wounded, including a law enforcement officer. (AP Photo/Manuel Balce Ceneta) Manuel Balce Ceneta, ASSOCIATED PRESS

Armed police prepare to enter the Washington Navy Yard as they respond to a shooting in Washington, Monday, Sept. 16, 2013. At least one gunman opened fire inside a building at the Navy yard. (AP Photo/Manuel Balce Ceneta) Manuel Balce Ceneta, ASSOCIATED PRESS

Law enforcement personnel walk through a gate into the Washington Navy Yard in Washington, Monday, Sept. 16, 2013, after at least one gunman opening fire. (AP Photo/Susan Walsh) Susan Walsh, AP