Eighth anniversary of the 9/11 attacks

Marta Waisman, right, of New York City, holds a photo of her daughter Gabriela, who lost her life in the attacks as people gather at Ground Zero during a 9/11 memorial ceremony Photograph: Pool/Getty Images

Family members of victims stand in the rain at the start of ceremonies marking the eighth anniversary of the attacks on the World Trade Center Photograph: Reuters

US President Barack Obama and first lady Michelle Obama observe a moment of silence for 9/11 victims on the South Lawn of the White House Photograph: Alex Wong/Getty Images

Family members of victims of the September 11 attacks pay their respects at the reflecting pool Photograph: Chang W.Lee /EPA

Firefighters hold the American flag as they gather to pay their respects at Ground Zero during a 9/11 memorial ceremony Photograph: Chris Hondros/Getty Images

People pause outside Ground Zero on the eighth anniversary of the September 11 2001 terrorist attacks Photograph: Spencer Platt/Getty Images

A woman holds a picture of a loved one before a ceremony marking the eighth anniversary of the 9/11 terrorist attacks on the World Trade Center in New York Photograph: Chris Hondros/Getty Images

Family members of victims stand in the rain at the reflecting pool placing flowers as people gather at Ground Zero during a 9/11 memorial ceremony Photograph: David Handschuh/Getty Images

Family members of victims pay their respects at the site of the twin towers on the eighth anniversary of the attacks on the World Trade Center Photograph: Gary Hershorn/Reuters

A police officer stands in front of flowers placed by Ground Zero reflecting pool Photograph: Chip East/AFP/Getty Images

US Vice President Joe Biden, right, his wife, Jill and New York City Mayor Michael Bloomberg, left, visit the reflecting pool at the 9/11 eighth anniversary commemoration ceremony in New York Photograph: Peter Foley/EPA

A police officer stands guard as relatives and friends visit the reflecting pool during the 9/11 eighth anniversary commemoration ceremony Photograph: David Handschuh/EPA

Relatives and friends visit the reflecting pool during the 9/11 eighth anniversary commemoration ceremony in New York Photograph: Chang W. Lee/EPA

People look at the World Trade Center construction site in New York, 11 September 2009 Photograph: Mary Altaffer/Associated Press