Former New York City Fire Commissioner Thomas Von Essen prided himself on being a different kind of leader. 

He spent more than two decades as a firefighter before he was at the helm of the Fire Department of New York (FDNY) from 1996 to 2002. And as such, it was not unusual to see Von Essen at the scene of a fire, even when he was commissioner. 

Doing so – joining FDNY members as they fought fires big and small— was often the "best part of the job," he told Fox News. But when he joined the mounting numbers of FNDY units that responded to the World Trade Center’s North Tower on Sept. 11, 2001, "You knew it was going to be a horrible, horrible day," he said.

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Von Essen, now 75, was in a car traveling along East River Drive that morning in 2001. He was headed for the FDNY offices when he received a radio call that "a small plane had crashed into the North Tower."

9/11 twin towers going up in flames after planes were hijacked

The second tower of the World Trade Center bursts into flames after being hit by a hijacked airplane in New York in this Sept. 11, 2001, file photograph. (REUTERS/Sara K. Schwittek)

"A couple of seconds later … I could see some smoke from the Trade Center," he recalled. "So we hit it a little faster and got there really quickly."

By the time he arrived, the windows in the lobby of the tower "had been blown out," he said. 

"The chiefs knew right away that they weren't going to be able to put the fire out, but they needed to help as many people as they could evacuate on the upper floors," Von Essen continued. 

Within minutes, as they learned more of the events unfolding throughout the country, "we realized we were under attack," he said.

Von Essen described in detail how the rest of the morning transpired, with the grim realization that the events were more than what the FDNY could handle, and the reality that, in only 102 minutes, both towers had collapsed. 

New York City Fire Commissioner cries as Rudy Giuliani speaks after 9/11

New York City Fire Commissioner Thomas Von Essen, left, rubs his eyes while then-New York City Mayor Rudolph Giuliani spoke at an NYFD promotions ceremony near NYFD headquarters in Brooklyn, New York, on Sept. 16, 2001. (HENNY RAY ABRAMS/AFP via Getty Images)

"The days got worse because the operation itself was just what you do, but the grief and the heartache … with all the families was the worst thing I’ve ever gone through," he continued. "These folks, so many of them lost loved ones – thousands of people lost loved ones."

The terror attacks on Sept. 11, 2001, claimed the lives of 2,977 victims, including 343 FDNY firefighters, 23 members of the NYPD and 37 Port Authority police officers. 

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For Von Essen, "it was personal," he said. "Every guy, firefighter, was something special to me – it wasn’t just a stranger."

NYC firefighters at a service for fallen fireman, Gregory Saucedo

Then-Fire Commissioner Thomas Von Essen kneels at a memorial service for Firefighter Gregory Saucedo of Ladder Co. 5, a victim of the World Trade Center disaster, at Mary Queen of Heaven Catholic Church in Brooklyn. (Todd Maisel/NY Daily News Archive via Getty Images)

Von Essen had planned to continue his role as commissioner under New York City Mayor Michael Bloomberg, who asked him to stay on, he said. But after 9/11, "it was too much."

"It was around the middle of November, I think. I was emotionally a wreck. I told Bloomberg, ‘I can’t. I can’t stay. I gotta go.’" 

Von Essen, a married father of four, left the FDNY that January and moved on to work with former Mayor Rudolph Giuliani. He then spent years working with Honeywell and Underwriters Laboratories before becoming an administrator with the Federal Emergency Management Agency (FEMA) – and working inside the new One World Trade Center. He agreed to the job before realizing the office’s location, he said. 

"Strange is putting it mildly," he said of working in virtually the same area where the attacks took place years earlier. 

Thomas Von Essen, former NYC fire commissioner remembering 9/11

Former fire commissioner Thomas Von Essen at the World Financial Center as New York marked the seventh anniversary of the attacks at the World Trade Center. (David Handschuh/NY Daily News Archive via Getty Images)

"Some days, it was terrible thinking about it. Some days, it was just full of pride. Some days, I'd get a sandwich and sit outside by the fountains and look at all the people that came there respectfully," he said. "You know, it was a mix of pride and pain."

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Von Essen still works part-time as a fire and safety consultant for major companies and is now a proud grandfather of eight. He still speaks with some of the FDNY brass he worked alongside on 9/11 and still feels choked up when thinking about the people they lost that day. 

"I don't think anybody had anything to be ashamed of that day, or embarrassed, or think that they did anything wrong. I think they wanted to get people up there as fast as they could to help people. That's what they did," he said. "They tried to get anybody out. They just couldn't get them out fast enough."