In Pictures: Remembering 9/11, two decades later

CTV National News: More details on 9/11 attacks For the first time since U.S. President Joe Biden's orders, the FBI declassified a document related to 9/11. Tom Walters reports.

TORONTO — WARNING: This story contains images that some people may find disturbing.

It has been 20 years since terrorists flew airplanes into the World Trade Center in New York and the Pentagon in Washington on Sept. 11, 2001, a series of attacks that changed the world as we know it.

Americans and Canadians alike are reflecting on the sacrifices made by firefighters, police, and other first responders who rushed to the scene to help.

They are also remembering how volunteers in Gander, N.L., and its neighbouring towns stepped up to help the passengers of airplanes that were diverted to Canada as news of the attacks spread.

Here are some photos that were taken in the aftermath of the 9/11 terrorist attacks.

Smoke billows through buildings in Manhattan as seen from Brooklyn after the collapse of New York's World Trade Center, Tuesday, Sept. 11, 2001. (AP Photo/Kathy Willens)

A firefighter moves through piles of debris at the site of the World Trade Center in New York, Tuesday, Sept. 11, 2001. (AP Photo/Graham Morrison)

People flee the scene near New York's World Trade Center, Tuesday, Sept. 11, 2001. (AP Photo/Diane Bondareff)

Pedestrians in lower Manhattan watch smoke billow from New York's World Trade Center on Tuesday, Sept. 11, 2001. (AP Photo/Amy Sancetta)

Pedestrians flee the area of New York's World Trade Center in lower Manhattan on Tuesday, Sept. 11, 2001. (AP Photo/Amy Sancetta)

A fireman screams in pain as he is rescued shortly after both towers of New York's World Trade Center collapsed following a terrorist attack, Tuesday, Sept. 11, 2001. (Robert Mecea/Newsday via AP)

Flames and smoke pour from a building at the Pentagon in Washington on Tuesday, Sept. 11, 2001. (AP Photo/Will Morris)

Two women hold each other as they watch the World Trade Center burns in New York Tuesday, Sept. 11, 2001. (AP Photo/Ernesto Mora)

The remains of the World Trade Center stand amid the debris in New York, Tuesday, Sept. 11, 2001. (AP Photo/Alexandre Fuchs)

People cover their faces as they escape the collapse of New York's World Trade Center on Sept. 11, 2001. (AP Photo/Suzanne Plunkett)