On 15th anniversary of 9/11, 'the grief never goes away'

The U.S. marked the 15th anniversary of 9/11 on Sunday, with victims' relatives reading their names and reflecting on a loss that still felt as immediate to them as it was indelible for the nation.

CLICK HERE TO WATCH President Barack Obama speaking to hundreds of service members, and relatives and survivors of the 9/11 attack on the Pentagon.

CLICK HERE TO WATCH hundreds gathering for name-reading observance at the Flight 93 National Memorial in Shanksville, Pa.