It's hard to believe we are already one year after the harder-to-believe massacre at Virginia Tech. I don't say "impossible-to-believe" because most of us Boomers have a long list of horrible events permanently etched into our cerebral cortices: the JFK, RFK, and MLK assassinations, Challenger evaporating in the morning sky, the shooting at Columbine, the Alfred P. Murrah Federal Building facade crumbling in Oklahoma City, and the Twin Towers somehow -- impossibly -- disintegrating on live TV. Alas, we know the ugly side of the Adidas slogan, "nothing is impossible."

Each generation, of course, experiences tragedies and disasters (and comedies and successes) across their lifetime. That's life. The never-ending flow of world events, cultural trends, fashions and fads rolls onward unabated, and it is up to each of us to interpret, react, process, and understand the impact.

What's interesting is that the events each generation shares during their adolescence -- roughly between the ages of 10 and 22 -- are the events that truly shape that generation. And while generations are typically about 20 years in length, the events experienced by the front half tend to overshadow those of the second half. That means April 16, 2007, at Virginia Tech will impact this cohort as much as the events of 9/11.

IN OUR STUDY of demography and generations, we see the impact of world events on each cohort. Those born in the 1920s and '30s remember things like Lindbergh's solo flight, followed by his son's kidnapping. World War II, the Holocaust, and Hiroshima are vivid memories that shaped that generation. Honor, duty, and a practical outlook sprung from those experiences.

Boomers, on the other hand, were affected by Vietnam, Watergate, women's lib, and Neil Armstrong's "giant leap" on the moon. They believe they can accomplish anything, but don't trust authority figures. Young adults of the Gen X cohort recall the Reagan assassination attempt, the fall of the Berlin Wall, and the birth of MTV. They were the latchkey kids born during the period of divorce and working moms, so they are fiercely independent and self-sufficient. Plus, they are much more multicultural, pragmatic, and techno-savvy than older generations.

The Millennial generation -- those between ages 5 and 25 this year -- have been "coming of age" during, among other things, the war on terror and random acts of violence at schools and other public places. The oldest in the cohort are recent college graduates or still in college themselves.

At the very least, the Virginia Tech massacre will be a touchstone event for that generation. The randomness of it ("it could have happened here") already has had an impact. There are groups on campuses across the country petitioning for permits to carry concealed weapons -- so the students can protect themselves. In ways we don't know yet, it will provide context for things they'll think and believe over the next 40 years. It will shape their world view and underlying values. It will contribute to a definition of that generation.

NOT TO GET too academic, but each of us, no matter our age or generation, experiences touchstone events in our own way. Part of how we respond is based on our life stage. If you are a 71-year-old grandparent who has experienced much, you view events differently from a 51-year-old parent with college-age children. If you are a 31-year-old with toddlers, you react differently from a 21-year-old. Your age, or life stage, matters.

Our reactions are also colored by the particular time in history. These days, for example, school shootings are still rare, but are becoming frighteningly more commonplace. Virginia Tech wasn't the first and, sadly, it wasn't the last. Where we sit in our place in history is both unique and revealing. It provides the context for our experiences and reactions.

Finally, each cohort responds differently because of differences among the generations. Those Silent and Boomer generation members may think about their feelings when JFK was killed. Generation X may think about Columbine. Each generation processes events through its own lens.

No matter how hard we try to understand the impact of April 16, 2007 on today's Millennials, we'll fail. In fact, while we older Boomers can console younger Millennials and tell them we understand. But we really don't. Not exactly.

All we know is that it will forever be a touchstone for this generation.
Matt Thornhill is president of the Boomer Project. He can be reached at matt@boomerproject.com or (804) 690-4837.