NEW YORK — Officials are working to determine why a huge construction crane that was being lowered to safety during strong winds came crashing down onto a New York City street, killing a pedestrian and crushing a row of parked cars. Three other people were hurt by debris, two of them seriously. But city officials said it could have been much worse.

“The fact is this is a very, very sad incident,” said Mayor Bill de Blasio. “We’ve lost a life, but if you go out there on the street as I did and see what happened here, thank God it was not worse.”

The mobile crane’s boom landed across an intersection, smashed several car roofs and stretched much of a block after the accident at a historic building in Lower Manhattan about 10 blocks north of the World Trade Center.

Robert Harold heard a crashing sound as the rig fell right outside his office window at the Legal Aid Society.

“You could feel the vibration in the building,” said Harold, who recounted seeing onlookers trying to rescue someone trapped in a parked car and seeing a person lying motionless on the street. After the collapse, the crane’s big cab lay upside-down in the snow with its tank-like tracks pointed at the sky.

Wall Street worker David Wichs was killed in the collapse. He was a mathematical whiz who worked at a computerized trading firm, his family said. Born in Prague, he had immigrated to the United States as a teenager and graduated from Harvard University, said his sister-in-law, Lisa Guttman.

Officials have not yet determined why the crane fell.

City building inspectors had been at the site only Thursday because the boom was being extended so it could reach farther onto the roof, de Blasio said.