September 11, 2011 (35 images)

Robert Peraza, who lost his son Robert David Peraza, pauses at his son's name at the North Pool of the 9/11 Memorial during tenth anniversary ceremonies at the site of the World Trade Center in New York on September 11, 2011. UPI/Justin Lane/Pool

A police officer's white gloved hand touches a name on the wall around the North pool of the 9/11 Memorial during tenth anniversary ceremonies at the site of the World Trade Center September 11, 2011, in New York. UPI/David Handschuh/Pool

New York Police, Fire, and Port Authority officers salute during the singing of the Star-Spangled Banner during the tenth anniversary ceremonies at the site of the World Trade Center on September 11, 2011, in New York. UPI/Aaron Showalter/Pool

Families visit the South Memorial Pool during tenth anniversary ceremonies at the site of the World Trade Center September 11, 2011, in New York. UPI/Robert Deutsch/Pool