For many it was the first time they'd seen adults cry; the first time they'd felt their security threatened; the first time the outside world had reached through the television screen and tapped them on the shoulder, figuratively speaking.
But for those born after the early 1980s, Islamist terrorism has become their tiger in the smoke – the main unpredictable threat to the nation, as was nuclear war in an earlier era. These so-called Millennials have grown up in an age of insecurity and that has made them different from their Generation X predecessors.
They are more team oriented than their elders. Polls show they strongly support the military. In some ways, they are more conventional in how they approach their lives. At the same time, they feel pressure to accomplish big things, to set the problems of the world right.
"One rule is that a generation's collective identity is decisively shaped by its location in history," said Paul Taylor, a Pew Research Center pollster, at a conference at the US Military Academy at West Point in New York earlier this year on Millennial attitudes. "Millennials are becoming adults during a decade bracketed by emergencies – 9/11 and the Great Recession."