New York(CNN) Fifteen years later, the scene is still seared into Hillary Clinton's memory.
"We saw this curtain of black smoke that was stretched across the island," Clinton recalled. "Occasionally it would be broken by a firefighter coming out. I remember one image so indelibly, dragging his ax, and it was as close to depiction of hell that I've ever personally seen."
Those were the things Clinton saw as she approached Ground Zero on September 12, 2001 -- the day after the country's worst terrorist attacks brought down New York City's World Trade Center and left thousands dead.
In an exclusive interview with CNN's Chris Cuomo, Clinton -- at the time New York's junior senator -- described the "sickening experience" of 9/11 and how she coped with the national tragedy by getting right to work.
When news broke of the first plane ripping through the north tower of the World Trade Center on the morning of September 11, Clinton had just left her house in Washington, D.C., and was on her way to the Senate. By the time she reached Capitol Hill, evacuations were already underway.
"So I gathered up my senior staff, we were just looking at each other with such total pain and confusion," Clinton said.
Soon after, they learned about a second plane hitting the south tower. "I got to a TV as quickly as possible to begin monitoring it. It was just sickening experience, Chris."
The next day, Clinton and her fellow New York senator, Chuck Schumer, got on one of the few planes that were allowed to fly that day and landed at LaGuardia Airport. After being taken to the city by helicopter, she and others began to walk toward where the twin towers had collapsed.
After seeing the devastation, Clinton said, she felt a heavy burden of the task ahead.
"There weren't that many survivors; the ones that did survive were grievously injured. The loss of life was overwhelming," she told Cuomo. "But it was also my job and the job of other officials to get our city and state and country what we needed."
In the days to come, Clinton, along with Schumer and others, would personally lobby President George W. Bush for funds to help the city rebuild. There were problems that lingered for New York residents well-past the immediate carnage of September 11, including health problems caused by the debris and toxic air that filled downtown, and victims who survived the attacks but were left with long-term injuries.
"I would meet these shattered lives of people where they were broken, but I saw so many of them strengthen and show such resilience. So I felt privileged," Clinton said. "It gave me an insight into the human spirit -- and I like to think the spirit of New York and America -- that I wish every American could understand."
On Sunday, Clinton will visit the Ground Zero memorial to pay her respects and observe the annual moment of silence at 8:46 a.m. ET -- the moment the first plane hit the north tower.
The CNN interview took place in New York City on Friday, shortly before Clinton told donors that half of Trump's supporters fall into "the basket of deplorables" -- a group of people who are racist, sexist, homophobic, xenophobic, and Islamaphobic.
The comments have caused an uproar and her Republican opponent, Donald Trump, has slammed her for the remarks.
She later said she regretted saying "half" of his supporters were "deplorables."
Clinton's sit-down with Cuomo comes just two months out from Election Day. Increasingly, the Democratic nominee and Trump have wrestled over the issue of national security and terrorism.
Addressing the news that North Korea conducted another nuclear test this week, Clinton cautioned that China has underestimated the regime.
"Up until relatively recently, I think they were under the impression that they could control their neighbor and they didn't want to crack down because they saw it as a useful card to play," she said. "If he gets a little crazy, maybe the South Koreans will move toward them a little bit, he gets a little crazier, maybe they can make some deals with the Japanese about things they want. It was a strategic calculation."
The former secretary of state said she believes the threats facing the country are not limited to ISIS but rather are part of a larger struggle against "a violent ideology -- a form of violent jihadism."
Trump's rhetoric, Clinton said, has only fueled the motivations driving ISIS.
"What unfortunately Donald Trump has done is made our job harder, and given a lot of aid and comfort to ISIS operatives and even ISIS officials who want to make this some sort of clash of civilization -- a religious war," Clinton said. "It's not, and it can't become that."
Clinton also warned that the message from Trump that has resonated with many Americans is entirely superficial.
"It's phony strength to not know what you're talking about and to make outrageous statements that will actually make our job harder, no matter how in the moment it sounds," she said. "Real strength is leveling with the American people and making it clear we will defeat ISIS."