รำลึกครบรอบ 13 ปีเหตุการณ์ 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.

President Barack Obama and First Lady Michelle Obama observe a moment of silence on the 13th anniversary of the 9/11 attacks at the White House, in Washington, 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.

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 911 attacks 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.

Visitors to the National September 11 Memorial observe the Tribute in Light, New York, Sept. 8, 2014.

The Tribute in Light rises behind buildings adjacent to the World Trade Center complex at the National September 11 Memorial, New York, Sept. 8, 2014.