WASHINGTON (WJLA) – Firefighter Stephen Gerard Siller had clocked out and was on his way to play golf with his brothers on a beautiful September day in 2001. Then he heard over his scanner that a plane had hit the North Tower of the World Trade Center. He turned around, got his gear, and drove to the Brooklyn Battery Tunnel, which had already been closed off because of security concerns.

Stephen strapped his equipment to his back and walked through the tunnel towards the towers. He died that day.

Nearly 20 years later, on Sunday morning in Arlington, Stephen's brother Frank began a journey to honor him and other first responder heroes.

The Tunnels to Towers Foundation, founded by Stephen's family shortly after 9/11, is already dedicated to providing for those heroes and their families. But as we approach the 20th anniversary of the terrorist attacks, a plan for a symbolic journey formed.

Frank, 68, will walk 537 miles — from the Pentagon to the site of the Flight 93 crash in Shanksville, Pa. to New York City — over the course of six weeks.

He laid a wreath at the Pentagon Sunday morning, and day one of his trek will culminate at the D.C. Armory.

At Sunday's kickoff press conference, Frank joked that he was going "12 miles in the wrong direction on the first day."

"No, it's the right direction, because I'm gonna go visit some very special firehouses, police stations, people who responded 20 years ago" to the Pentagon, he said.

Tunnels to Towers has several programs and events benefitting heroes, but "our first mission is to make sure we never forget what happened 20 years ago," Frank said Sunday. "We must honor the sacrifice."