NEW YORK (CBSNewYork) — More than 300 firefighters from around the world climbed the stairs of a World Trade Center skyscraper Sunday morning in honor of their brethren killed on 9/11.

The 72-story climb was held at 4 World Trade Center.

READ MORE: Unlicensed Long Island Massage Therapist Accused Of Touching Clients Inappropriately

“Good cause. … Never forget that these guys gave the ultimate sacrifice,” one firefighter from Coral Gables, Florida, told WCBS 880’s Peter Haskell.

The morning started with a moment of silence at the 9/11 Memorial. Then the 343 firefighters began their climb.

The number of participants matched the number of FDNY members killed on 9/11. Photos of each of them lined the stairwell at 4 World Trade Center on Sunday.

READ MORE: Police Seek Suspect In String Of Burglaries In Lower Manhattan

Sweaty and spent, finishers were greeted at the top.

The event was started by firefighters Chris Barber and John Mills.

MORE NEWS: Man Shot To Death In Elmont, Nassau County Police Investigating

“Personally, I lost my father in the South Tower, so obviously he runs through my head,” Mills said.