The crash occurred shortly before 2 p.m. (1800 GMT) on a rainy, foggy day at the 50-story AXA Equitable Center at 787 Seventh Avenue. Dozens of emergency vehicles swarmed the busy area, a few blocks north of Times Square.
The city fire department said on Twitter around 2:40 p.m. that one unidentified person was killed. Media reports said the person was the helicopter pilot.
Nathan Hutton, who works in information technology for the French bank BNP Paribas on the 29th floor, said the building shook when the helicopter slammed into the roof.
"It felt like you were just standing there, and someone takes their hand and just shoves you," he said. "You felt it through the whole building."
New York Governor Andrew Cuomo, who was at the scene soon after the crash, told reporters that it appeared a helicopter attempted a forced emergency landing on the roof and that no one inside the building had been injured. It was not clear if the weather was a contributing factor.
The Federal Aviation Administration said in a statement that the aircraft was an Agusta A109E, a twin-engine, lightweight helicopter. The pilot was the only person aboard, and FAA air traffic controllers did not handle the flight, according to the agency.
The National Transportation Safety Board will investigate the cause of the crash, the FAA said.
Melvin Douglas, 50, who was selling umbrellas on the street, said he heard a "rumble" when the helicopter crash landed.
"I didn't see it, but I felt it," said Douglas. "Smoke was on top of the building."
A fire that broke out on the roof was quickly brought under control, the fire department said. The building was evacuated after the crash.
"Phenomenal job by our GREAT First Responders who are currently on the scene," U.S. President Donald Trump said on Twitter after being briefed on the crash. "The Trump Administration stands ready should you need anything at all."
The AXA Equitable Center is more than 750 feet (229m) tall and was built in 1985. A roof helipad is not listed as one of the building's amenities on its website.
In addition to BNP Paribas, the building houses offices for a number of other corporate tenants, including law firms Willkie Farr & Gallagher and Sidley Austin and investment manager New Mountain Capital. Le Bernardin, one of New York City's most celebrated restaurants, is also located in the AXA building.
The skyscraper is managed by the Los Angeles-based CommonWealth Partners. Reached by telephone, LeAnn Holsapple, the office manager for CommonWealth, said the company had "no comment at this time."Nearly a month ago, a chopper crashed into the Hudson River in New York City shortly after taking off from Manhattan, injuring two people. A sightseeing helicopter went down in New York City's East River in March 2018, killing five passengers.