The pilot of a helicopter has died after it crash landed on top of a skyscraper in Manhattan.
The helicopter burst into flames on hitting the AXA Equitable Center, but there were no other casualties.
The pilot has been identified as Tim McCormack, a veteran aviator. An investigation is under way.
Eyewitnesses said the building shook with the impact and they were reminded of the plane attacks on the city in September 2001.
Officials quickly ruled out any terrorist element to the crash.
It occurred on a rainy and foggy Monday afternoon at 787 Seventh Avenue, just north of Times Square.
The twin-engine Agusta A109E, carrying only the pilot, had taken off from a heliport on Manhattan’s east side at 13:32 local time. It was reportedly heading to Linden Airport in New Jersey.
Eleven minutes later it plunged into the top of the 54-storey office building, in what was described as a forced or emergency landing.
New York City Mayor Bill de Blasio said the helicopter was “pretty obliterated… it was obviously a very hard hit”.
National Transportation Safety Board officials will be looking into why the helicopter, which officials said was engaged in “executive travel”, was flying in such poor weather.
Mr de Blasio said it was “an unusual situation for sure”, and the helicopter would have needed special permits from LaGuardia Airport in the New York City borough of Queens.
The Federal Aviation Administration said its controllers would not have been handling the flight.
The building is about half a mile from Trump Tower, and airspace has been under flight restrictions since that building’s owner Donald Trump became president.
New York State Governor Andrew Cuomo said: “If you’re a New Yorker, you have a level of PTSD (post-traumatic stress disorder), right, from 9/11. And I remember that morning all too well.
“So as soon as you hear an aircraft hit a building, I think my mind goes where every New Yorker’s mind goes.”
President Trump said the crash was “a big tragedy” and “a very sad event”.
Eyewitness Nicolas Estevez told Reuters he “saw the explosion and the smoke coming out” and it had reminded him of 9/11. A 12in (30cm) piece of metal landed on the pavement just feet away, he said.
Michaela Dudley, of Hoboken, New Jersey, who works in the building, described feeling “a small tremor”.
“I started hearing the blare of sirens and knew something bad had happened,” the 30-year-old lawyer said.
“There was an announcement for us to leave the building. I grabbed my backpack and cellphone. The stairwell was packed with people trying to get out and so it was a really slow process. We didn’t know what was happening so people were getting a bit panicky.”
Tim McCormack was described as a highly trained, veteran pilot who was also a volunteer firefighter.
ABC News carried a statement it said had been sent on behalf of the McCormack family, which read: “Our family lost a great man today when my brother lost his life doing his job. He was a caring and compassionate man who put others first over himself.”
It said he had landed on the roof “so that it didn’t impact anyone else’s life except his own. My brother was a true hero”.
Some US media have said Mr McCormack was also involved in setting down a helicopter safely after a bird strike in 2014.
American Continental Properties, which the helicopter is registered to, said it mourned the loss of Tim McCormack “who has flown for us for the past five years. Our hearts are with his family and friends”.
Paul Dudley, Linden Airport manager, said the pilot had “tremendous local knowledge, having flown in this area for many years… Something must have happened to overwhelm him.”
The East Clinton Fire Department said Mr McCormack was “a dedicated, highly professional and extremely well-trained firefighter. Tim’s technical knowledge and ability to command an emergency were exceptional.”