In their own words: Firsthand accounts from September 11, 2001

NEW YORK -- Sept. 11, 2001, changed the world as we know it, from the way we live our everyday lives to the mournful remembrances that honor the victims each year amid vows to "never forget."

In the video player above, watch firsthand accounts from those who were in Lower Manhattan on that fateful day, with commentary from then-anchor Bill Beutel. (Warning: This contains images that some may find disturbing.)

Each year, relatives of the victims descend on ground zero in Lower Manhattan, and the events of that terrible day and the weeks, months and years that followed are never forgotten, nor are the memories of those killed by terrorists in hijacked planes.

Here's how the terror attacks unfolded on September 11, 2001.

Additionally, we remember all those who have died from 9/11-related illnesses from their heroic work at ground zero and those who suffer today.

September 11 still shapes American policy, politics and everyday experiences in places from airports to office buildings, even if it's less of a constant presence in the public consciousness after more than two decades.

WATCH: How a reporter and photographer escaped the Twin Towers collapse

Eyewitness News reporter N.J. Burkett and photographer Marty Glembotzky rushed down to the World Trade Center on September 11, 2001. While shooting a standup right below the burning towers, the first tower began to collapse.

The 9/11 commemorations are by now familiar rituals, but each year at ground zero, victims' relatives infuse the ceremony with personal messages of remembrance, inspiration and concern.