CHICAGO (CBS) — Fifteen years and a day after 9/11, one of the survivors of World Trade Center attack spoke about that day at his son’s high school in LaGrange Park.

“The whole building rocked,” said 46-year old Stu Breslow, father of 17-year old Nazareth Academy senior Brendan Breslow.

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Fifteen years ago, Stu Breslow was an employee of Lehman Brothers and was at his desk on the 40th floor when the first plane hit the World Trade Center north tower, about 40 stories above him.

“I was on conference call with colleagues in London on a speakerphone, and it was very, very unnatural. So I immediately jumped and ran to the stairwell,” he says.

Breslow said, at dinner on Sunday, the 15th anniversary of the attacks, his wife said a prayer and mentioned that the couple’s two youngest children would never have been born had their father not made it down the stairs in time to get out of his burning skyscraper.

“There was strange calm among all the people that were in the stairwell, and there was not mass hysteria,” he said.

Breslow says he visited the 9/11 memorial and museum for the first time last year and that it sent chills down his spine to hear the voice recordings and see some of the artifacts.

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He said he does not have any major lingering effects from 15 years ago, “but, I am very easily startled from any type of loud noise or bang.”

Nazareth Academy students, who were not born yet or not old enough to remember the 9/11 attacks, said it was good to hear a first-hand account of someone who was at Ground Zero.

“We have learned the facts, we have seen the footage, but we have never had the opportunity to actually enter in to someone’s mind who was there and who experienced the tragedy,” Brooke Gawel said.

Daphne Bigelow, 16, said although she was too young to remember 9/11, Breslow’s talk resonated with her.

“The way that he described it seemed very extremely breathtaking almost, and kind of like this shock of an idea that this is really happening, I can’t believe this happened,” she said.

Breslow encouraged the students to be vigilant, to respect first responders and the military, and to be proud Americans.

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“Hopefully they take away the history lesson, and they take away the signs that, or at least the vigilance that this could happen again, and they just need to be aware,” he said.