An FDNY firefighter from Bethpage was killed in the line of duty Thursday afternoon after he fell five stories through the roof of a burning building, officials say.

FDNY Commissioner Daniel A. Nigro said Firefighter William N. Tolley, 42, was deployed to the two-alarm fire at 1615 Putnam Ave. around 2:20 p.m. He says Tolley was operating as the outside ventilation firefighter near where the bucket from Ladder 135 was located.

"Firefighter Tolley fell five stories from the roof and he perished about 20 minutes into fighting that fire," Nigro said.

The circumstances of the fall are under investigation by the Safety Command and the Bureau of Fire Investigation, according to Nigro.

The FDNY says Tolley was transported to Wyckoff Heights Medical Center in Brooklyn, where he died from his injures.

"I join with all FDNY members in honoring the memory of our brother who unfortunately lost his life in the line of duty earlier today," said Jake Lemonda, president of the FDNY Uniformed Fire Officers Association. "This is an extremely dangerous job that our dedicated members put their lives on the line every day to protect the residents of the City of New York."

Michael Gleason, of Bethpage, said Tolley often talked about his work. He loved the job, he says, and accepted the risks that came with it.

New York City Mayor Bill de Blasio said the entire city stands with Tolley's family after the tragedy.

Tolley was a member of Ladder 135 for 14 years and also served as a volunteer for the Bethpage and Hicksville fire departments. He is survived by his wife Marie, 8-year-old daughter Bella, brother and parents.