Thousands followed the footsteps of a firefighter who died in the September 11th attacks Sunday in the Tunnel To Towers run that has become an act of remembrance and charity.

Runners followed the path taken by firefighter Stephen Siller on 9/11, retracing his sprint through the Brooklyn Battery Tunnel to the World Trade Center while carrying 60 pounds of gear.

Siller died when the south tower collapsed.

The 5K run and walk was created in his memory the year after the attacks. Race organizers raised money in the name of the event, first for a number of local initiatives, and then expanded to helping military personnel returning home from duty.

"The service men and women, who after September 11th who went and joined the service just because of what happened in New York City, so this is our thank you to them and their families and to the first responders to say that, you hear the words 'Never Forget,' we really mean we’ll never forget. That’s why we’re here today."

The race started out with just 300 runners in its first year and has grown to more than 30,000. The Brooklyn Battery Tunnel is closed until about 3 p.m. Sunday.