A helicopter has crashed into New York City’s East River and flipped upside down in the water, killing two of the six people aboard and leaving three others in critical condition, officials said.

Video taken by a bystander and posted on Twitter shows the red helicopter land hard in the water and then capsize, its rotors slapping at the water.

The helicopter, a private charter hired for a photo shoot, went down near Gracie Mansion, the mayoral residence. One person, the pilot, freed himself and was rescued by a tugboat, officials said.

The passengers were recovered by police and fire department divers, who had to remove them from tight harnesses while they were upside down, Fire Commissioner Daniel Nigro said.

Witnesses on a waterfront esplanade near where the aircraft went down said the helicopter was flying noisily, then suddenly dropped into the water and quickly submerged. But the pilot appeared on the surface, holding on to a flotation device as a tugboat and then police boats approached.

NYC Helicopter Crash
The scene of a helicopter crash in the East River in New York (New York City Police Department/AP)

“It’s cold water. It was sinking really fast,” Mary Lee, 66, told the New York Post. “By the time we got out here, we couldn’t see it. It was underwater.”

News footage showed one victim being loaded into an ambulance while emergency workers gave him chest compressions.

A bystander, Susan Larkin, told The Associated Press that she went down to see rescue boats in the river and a police helicopter circling overhead, hovering low over the water.

“You could clearly see they were searching,” she said.

A Federal Aviation Administration (FAA) spokeswoman said the Eurocopter AS350 went down just after 7pm local time. The aircraft was owned by Liberty Helicopters, a company that offers both private charters and sightseeing tours popular with tourists. A phone message left with the company was not immediately returned.

The cause of the crash is unknown. The FAA and the National Transportation Safety Board are investigating.

Officials did not immediately release the names of the pilot or passengers or say how the two passengers died.

The helicopter was recovered in the rescue operation and towed to a pier.