A firefighter looks at a memorial mural on the outside of firehouse Engine 10 Company 10 adjacent to the World Trade Center in New York, Thursday, Sept. 11, 2014. Three hundred forty three New York firefighters were killed in the terrorist attacks of Sept. 11, 2001. (AP Photo/Mark Lennihan)

Photos: World Trade Center

Thirteen years after 9/11 forever changed the New York skyline, officials say developments at the World Trade Center are on track and on bud…

In this Sunday, Sept. 7, 2014 photo, 1 World Trade Center towers above the lower Manhattan skyline in New York. Thirteen years after 9/11 forever changed the New York skyline, officials say developments at the World Trade Center are on track and on budget. (AP Photo/Mark Lennihan)

Photos: Nation remembers 9/11

The nation pauses Thursday to mark the thirteenth anniversary of the Sept. 11, 2001 terror attack.

New York City skyline, Sept. 11, 2014.

Remembering 9/11

The nation will pause Thursday to mark the 13th anniversary of the Sept. 11 terror attacks.