Where were you on 9/11? Most of today’s high school students were not yet born and most college students are too young to remember when 19 Islamic extremists carried out the deadliest attacks on American soil in United States history.

On that day in 2001 that dawned as a stunning fall prelude with a promise of endless blue skies and high-60s temperatures, Hartford HealthCare CEO Jeff Flaks was an executive at St. Vincent’s Hospital in New York attending an annual capital and operating budget session.

“We heard a noise,” he says. “Initially, it wasn’t that alarming. But we walked outside shortly thereafter and saw some degree of devastation. Moments later, we saw the second plane fly directly into the World Trade Center. It’s a vision I’ll never forget.”

An estimated 2,750 would be killed when the hijacked planes were flown into the Twin Towers, one and then another, destroying what were at the time the world’s tallest buildings. Suicide attacks killed 184 more at the Pentagon in Arlington, Va., and 40 in Pennsylvania, where one of the hijacked planes crashed after a passenger revolt.

In New York, as first-responders streamed toward the World Trade Center, St. Vincent’s became the city’s emergency response center. Hospitals, the safety nets for their communities, tend to be at the center of all when disasters strike.

“I saw the very best of humanity,” says Flaks. “I saw people donating blood, people voluntarily looking to donate corneas. People would do anything they possibly could. I saw the community come together.”

Today, the 9/11 Memorial offers a solemn tribute with its two giant waterfalls and reflecting pools set within the Twin Towers’ original footprint. St. Vincent’s, old enough to have treated victims of the 1849 cholera epidemic, closed in 2010.

The nation moves on, but never forgets.

“It was indelible to me in terms of what it meant,” says Flaks. “It makes me understand why all of our healthcare system has to be ready to partner with government, with community, at a moment’s notice to do the right thing.”