9/11 25th anniversary live updates: Families to gather for ceremonies at World Trade Center, Pentagon, Shanksville

On the morning of Sept. 11, 2001, 34-year-old New York City firefighter Stephen Siller had just finished his overnight shift when he heard a call come in on the scanner.

"He immediately knew something was awry," so he drove to his firehouse in Brooklyn, his son, Stephen Siller Jr., told ABC News.

"When he got there, he realized his whole unit had responded [to the World Trade Center]," Siller Jr. said. "So he grabbed his gear, threw it in his truck and started to make his way to the World Trade Center. But on 9/11, they shut down every entryway into Manhattan."

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Steel from ground zero carries 9/11 sacrifice across AmericaStephen Siller Jr. honors his father’s 9/11 sacrifice by carrying World Trade Center steel across America to preserve his legacy.

ABC

He parked his car by the Brooklyn Battery Tunnel, Siller Jr. said, put about 60 pounds of gear on his back, and ran through the tunnel to the South Tower of the World Trade Center.

Stephen Siller was among 343 New York City Fire Department members killed on 9/11. He was survived by his close-knit siblings, his wife Sally, and his five children, including Stephen Jr., who was 9 months old.

Siller Jr., now 25, doesn't have his own memories of his father, but he's poured his energy into honoring those who died on 9/11.

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Chef Don Pintabona spent years cooking up the finest dishes for celebrities, Wall Street brokers and other VIPs at the Tribeca Grill in downtown Manhattan, but nothing could have prepared him and the rest of the city's restaurant community for their biggest job.

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Meet the chefs who kept Ground Zero workers fueled after the 9/11 attacksIn the weeks after the World Trade Center was destroyed, city chefs and thousands of New Yorkers banded together to help feed Ground Zero workers around the clock.

ABCNews.com

In the hours after the World Trade Center was attacked and destroyed on Sept. 11, 2001, Pintabona said he and many other chefs, caters, food service workers and others all yearned to help the city in some capacity with their skills, but didn't immediately know how.

But through quick thinking, organizing and the generosity of thousands of New Yorkers, Pintabona and the other restaurant members put together a massive operation that fed Ground Zero workers around the clock for two months after the attacks.

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Jack Moran Jr. spoke with ABC News Live about the legacy of his friend Welles Crowther, a 9/11 hero who has been dubbed the "man in the red bandana.”

“He saved the lives of 18 people -- he’s a hero,” Moran said. “And it’s very important to know his story.”

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Friends and family honor the legacy of 9/11 hero Welles CrowtherWelles Crowther, dubbed the "man in the red bandana," is remembered by his friend Jack Moran Jr. for his courageous acts on September 11.

ABCNews.com

A one-hour ABC News special called "9/11 Tribute in Light: Live from Lower Manhattan" will premiere at 8 p.m. on Friday, led by "World News Tonight" anchor David Muir, "Good Morning America" co-anchor Robin Roberts and anchor Diane Sawyer.

The special, produced in collaboration with the 9/11 Memorial & Museum, honors the victims, victims’ families, survivors and first responders.

You can watch the special on ABC, Disney+, Hulu, National Geographic, ABC Owned Television Stations livestreams and ABC News Live.