NEW YORK (CBSNewYork) There are those who remember the 9/11 terror attacks and those who witnessed it all.

No one more so than the man thrust with command of rescue operations, current FDNY Commissioner Daniel Nigro.

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“It was 17 acres of horror,” Nigro told CBS2’s Mary Calvi. “It was unimaginable, the chaotic scene.”

Nigro rushed to the World Trade Center, where the FDNY set up a command post.

Soon afterwards, the chief of the department was killed by falling debris, leaving his deputy Nigro in charge.

“How was it that you were one of the lucky ones?” Calvi asked.

“I had started circling the building and left the command post to get a view of the damage, especially of the South Tower after seeing parts of the plane go right through it. Being on the other side of the building, I was in a position where I could find safety,” Nigro said.

Complete Coverage9/11 Twenty Years Later

Nigro was immediately thrust into the command of rescue operations of an attack of historic proportions.

“Calls were coming in rapidly from people that were above in great danger, and we were trying to reach them,” he said. “It was our best day in the way that we rescued so many people, but then it ended as our worst day.”

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Nigro stood with his members on those days and the weeks and months that followed.

Since that fateful day, much has changed in the department. Now as fire commissioner, Nigro is looking ahead.

He is New York City’s highest ranking government official who was at the World Trade Center that day.

“We were not afraid to look at ourselves critically afterwards,” explained Nigro.

Today, operational readiness is at the forefront.

“Our communications are better — our radio communications, our ability to communicate with all the other city agencies that we need to communicate with. We developed a center for terrorism and emergency preparedness, which creates scenarios that we train in-house and with our sister and brother agencies — whether it’s federal, state or city agencies — on how we would react to possible future attacks,” he said.

As we commemorate 20 years, there is one thing that will not go unnoticed.

“There is nothing more heroic than what your members did that day,” said Calvi. “No one turned away. No one decided, ‘I’m not going in there.'”

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“I could see it in the eyes, especially of senior members, who knew they might not come out of the building,” Nigro said. “But as you said, of the 750 or so members that responded before the collapse, every person who was asked to enter those buildings entered bravely and did what they promised they would do when they came into the department.”

Mary Calvi