Some days live on in our memories forever. In my parents’ lives, Pearl Harbor was one of those days. The death of FDR was another.

In my lifetime, those days include the assassinations of John F. Kennedy, Martin Luther King, Jr., and Robert F. Kennedy.

Then came September 11. I live directly across the New York Harbor from lower Manhattan. I heard the first plane crash. I ran to the harbor and arrived just in time to see the second plane crash into the second World Trade Center building. I saw it. That sight is seared into my memory.

The events of the day were unforgettable. The sounds (sirens and jets), the smell of burning plastics, the scenes we saw on television—the bodies flying through the air.

For many weeks afterwards, there were signs posted in public places in NYC: photographs of men and women who were missing. “Have you seen…?”

There will be debates and books for years about why it happened. It was terrorism, for sure. That day led us into a war that lasted for 20 years and cost even more lives. It changed the act of taking a flight, imposing security measures.

For the thousands of innocent men and women who died that day, it was a tragedy. I mourn for the children who lost parents and grandparents, for those who lost husbands and wives, brothers and sisters. I mourn for the firefighters and police officers who ran to the burning buildings and lost their lives. It is a sad day of remembrance.