At the station house nearby, memorial candles and flowers crowded the door.

An official with knowledge of the matter said that Mr. Tolley was either in or around the bucket at the top of the fire ladder when he fell.

Michael T. Vogel, a neighbor, said he had heard a loud noise followed by yelling.

“I heard everyone shouting, ‘Get back, get back,’” said Mr. Vogel. When he went out onto the street, he said, there were at least a dozen firefighters surrounding the man.

A red tent was later placed over the area.

Three other people were taken to the medical center with minor injuries, officials said.

Mr. Tolley, of Bethpage, N.Y., on Long Island, is survived by his wife, Marie, and his 8-year-old daughter, Isabella, officials said.

“Everyone is in a state of shock and grief,” Mr. de Blasio said. “To his family, we say we will stand with you, not only today but in the days ahead.”

James Slevin, the president of Uniformed Firefighters Association, the union that represents New York City firefighters, said Mr. Tolley was a hero.