Tracing the steps of the off-duty firefighter who raced in full gear toward Ground Zero -- and ultimately, to his death -- during the 9/11 terrorist attacks, more than 30,000 runners from across the globe Sunday made their way through the Hugh L. Carey Tunnel.

The 14th annual Stephen Siller 5k Run & Walk culminated in a rally held in the long shadow of the newly erected One World Trade Center tower, one of many symbols of rebirth in lower Manhattan.

Participants included children who had not yet been born when the Twin Towers fell, 2,500 cadets from the U.S. Military Academy at West Point and members of volunteer fire departments from around the region.

"There's nothing to look at but the walls, and you have a chance to reflect on what he was thinking about," Bill Byrnes, 53, of the Southold Fire Department, said of running through the tunnel and what Siller experienced that day.

Emerging from the darkness and seeing the photographs of the 343 fallen Bravest on banners held by fellow FDNY firefighters in dress blues was even more emotional, Byrnes said.

"Everybody knows the number 343, but to see every picture, it's really amazing," he said.

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Siller, 34, a Rockville Centre native and Staten Island resident, had just finished a shift the morning of Sept. 11, 2001, when he learned a plane had crashed into the World Trade Center. Blocked by vehicle traffic and unable to drive back to Manhattan, he strapped on 60 pounds of gear and sprinted nearly 2 miles through what was then known as the Brooklyn-Battery Tunnel.

"We just wanted to do something in honor of our little brother," said Frank Siller, chairman and chief executive of the Stephen Siller Tunnel to Towers Foundation, which now has an international reach and has raised $50 million since its 2002 inception. "I feel pretty blessed that Stephen's sacrifice has gotten us to a point where we're doing so much good."

At the rally, former Mayor Rudy Giuliani said the event's massive turnout year after year was evidence that Stephen Siller, a father of five, and other first responders will never be forgotten.

FDNY Commissioner Daniel Nigro called Siller "one of the bravest of the Bravest."

Retired U.S. Army Sgt. Matthew Melancon, a double amputee who lost his legs in a 2011 IED blast in Afghanistan, ran through the tunnel, then doubled back to walk it a second time on his prosthetic blades.

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"It's been a long road to recovery for me," said Melancon, 25, of Cedar City, Utah. Melancon noted that he was just a sixth-grader at the time of the 9/11 attacks, which changed the course of his life.

Katherina Kasap, 28, a volunteer with the New Hyde Park Fire Department, said the attack inspired her to be a firefighter. She wore what she estimated was 30 pounds of firefighting gear. She said that as she ran, she thought about Siller and "what people are willing to do for their country."

This year, for the first time, there were banners with the images of the 23 NYPD officers and 37 Port Authority police who died at Ground Zero.

Sunday's race was expected to raise $1 million for charitable causes, including aiding in the superstorm Sandy rebuilding effort, running a traveling 9/11 exhibit that visits schools across the nation and building technologically advanced "smart homes" for catastrophically injured war veterans.