"The smells. Decomposition. Burning flesh. Smoke. Destroyed buildings," he said.
Back in September 2001, Schapelhouman was part of a California search and rescue team sent to New York City after the 9/11 attacks.
An experience, he says, is almost indescribable.
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Something he's never been able to forget.
"The gates of hell is probably a good way to describe it. Or war of the worlds," Schapelhouman said.
But beyond the mental toll, for Schapelhouman and his teammates, there was also a physical price to pay.
Out of the 68 people on Schapelhouman's team, 47 of them, or about 70%, have suffered health issues in the years after 9/11.
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Those health issues, Schapelhouman believes, were caused by the so-called plume that engulfed the rubble of the World Trade Center for weeks after the attack.
"We realized then that we had gotten ourselves into something worse than anybody had anticipated," he said.
While the health problems have gotten better over time for some of his teammates, for others, including himself, Schapelhouman says they still persist to this day.
But despite the toll it took both mentally and physically, Schapelhouman says he wouldn't hesitate to do it all again.
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Not just for those he helped in the weeks after the disaster, but for everyone else too.
"Freedom isn't free, and this could happen again. It may not look the same, but there's always that risk in a free society," Schapelhouman said.