Mario Tama is a New Yorker who will never be able to forget Sept. 11, 2001.

The nascent photographer has just moved to the Big Apple in the summer of 2001 to take a job with the stock photo agency Getty Images, when he got a call on the morning of Sept. 11 to get down to the World Trade Center.

"One of my editors was frantically screaming into the phone, ‘A plane just hit the towers, a plane just hit the towers'," Tama recounted to CTV's Canada AM from New York Tuesday.

Tama says while he didn't yet know what was happening, he grabbed his gear and rushed out of his Lower East Side apartment and headed downtown. When he got there, he looked up.

"I saw this huge gaping hole in the North Tower and I remember just thinking to myself, ‘This is war'," Tama remembers.

For the next few hours, Tama shot some of the most memorable images of that day, from the photos of the burning towers belching black smoke into the blue sky, to the massive cloud caused by the tower collapse, to the dusty aftermath, when every block of the downtown was covered with the white cloudy debris.

He says in that first hour, he watched the towers burn from about a block away, standing alongside dozens of others who were mesmerized by the scene.

"Some people were gazing up, watching people jumping off. Other people were fleeing, other people were crying and victims were coming out. All of this was happening at the same time, so it was very chaotic," Tama says.

When the first tower fell, Tama remembers everybody running for their lives.

"There was a tornado cloud of debris that chased us down the street. We all thought we were going to die," he says.

As the cloud came over him, Tama says he dove around a corner and huddled down with two strangers.

"There was an instant blackout, and all three of us just began to pray. One of the men prayed in Spanish and the other two of us prayed in English," he remembers.

Tama was able to keep shooting, taking photos of the men he was with, images that became symbolic of that morning.

For the next few weeks, Tama continued working, shooting photos of the Ground Zero cleanup, starting first with the search for survivors.

He says the most emotional photo he shot of the cleanup was an image of a "bucket brigade": A group of firefighters standing in a row, removing debris by hand and bucket and passing the bucket down the line. For some reason, that image has always affected him.

"To see this kind of hope and humans coming together top help each other in the midst of such a disaster was, to me, a defining moment," he says.

The events of 9-11 turned out to be Tama's introduction to war photography.

Tama later went on to take a number of award-winning photographs of the aftermath of Hurricane Katrina and the start of the Iraq War, but he has said that 9-11 remains the most shocking thing he's ever covered.