Remembering 9/11

President Barack Obama bows his head during a moment of silence at the Pentagon during a ceremony to mark the 13th anniversary of the 9/11 attacks, Sept. 11, 2014.

President Barack Obama, First Lady Michelle Obama, Vice President Joe Biden, and others observe a moment of silence to mark the 13th anniversary of the 9/11 attacks, on the South Lawn of the White House, in Washington, Sept. 11, 2014.

Jose Colon, of New York, looks up at 1 World Trade Center before a ceremony marking the 13th anniversary of the 9/11 attacks, Sept. 11, 2014, in New York.

A woman grieves at the site of her husband's inscribed name at the edge of the North Pool during memorial observances on the 13th anniversary of the 9/11 attacks at the site of the World Trade Center in New York, Sept. 11, 2014.

Hattie Wilson places her hand over her heart during the singing of the National Anthem as she mourns her nephew Det. Joseph Seabrook during memorial observances held at the site of the World Trade Center in New York, Sept. 11, 2014.

From left, President Barack Obama, Defense Secretary Chuck Hagel and Joint Chiefs Chairman Gen. Martin Dempsey participate in a ceremony at the Pentagon, Sept. 11, 2014, to mark the 13th anniversary of the 9/11 attacks.

A woman reaches out to touch a rose on one of the benches of the Pentagon Memorial at the Pentagon, Sept. 11, 2014.

Friends and family of Wayne Russo hold up photographs of him as his name is read aloud during memorial observances held at the site of the World Trade Center in New York, Sept. 11, 2014.

Sam Pulia, mayor of Westerchester, Illinois and a former police officer salutes the name of his cousin, New York firefighter Thomas Anthony Casoria, who was killed in the South Tower, prior to the memorial observances held at the site of the World Trade Center in New York, Sept. 11, 2014.

Barry Hogan prays at the Empty Sky Memorial at Liberty State Park, Sept. 11, 2014, in Jersey City, New Jersey.

Visitors to the Flight 93 National Memorial hold a giant flag as they participate in a sunset memorial service at sunset in Shanksville, Pennsylvnia, Sept. 10, 2014.

The Tribute in Light rises behind the Brooklyn Bridge and buildings adjacent to the World Trade Center complex, Sept. 10, 2014 in New York.