Federal investigators headed to New York on Monday after a helicopter crashed into the city's East River on Sunday evening, killing five people.
Of the six people on board, only the pilot escaped alive, according to New York City Police.
Two of the five passengers had died by the time rescuers arrived, while the three others were cut free from the helicopter's harnesses and later died in hospital, according to authorities.
Police named the pilot on Monday as 33-year-old Richard Vance. He was able to free himself from the sinking helicopter and was rescued by a passing tugboat, police said.
After being treated in hospital, Mr Vance was soon released in good condition.
"It's a great tragedy," said New York Fire Commissioner Daniel Nigro. "It took a while for the divers to get these people out."
According to Mr Nigro, the helicopter was inverted in 50 feet of water when the divers reached it.
The conditions were challenging, he said, with river currents of four miles an hour and freezing cold water – less than 5C.
The passengers were in tight harnesses, which had to be cut before they could be freed, explained Mr Nigro.
No details of the passengers' identities have yet been released.
New York City Police Commissioner James O'Neill said the aircraft was registered to Liberty Helicopters, a sightseeing and charter service in New York, and was on a private charter "photo shoot".
On its website, Liberty describes itself as "the largest and most experienced helicopter sightseeing and charter service in the Northeast". The company claims to deliver "unparalleled safety records".
According to his Linked In profile, Richard ('Rick') Vance lived in Danbury, Connecticut, just north of New York City, and has worked as a pilot for Liberty Helicopters since April 2016.
Between 2012 and 2016, according to his profile, Mr Vance was an Assistant Chief Flight Instructor for Northeast Helicopters, a helicopter school in Connecticut.
The Eurocopter AS350 went down near the northern end of Roosevelt Island at about 7pm local time, according to the Federal Aviation Administration, which is investigating the crash.
Video posted to Twitter shows the helicopter landing on the surface of the river before tipping over as the rotor blades slice through the water.
Witnesses of the crash reported seeing the boat quickly sink beneath the surface.
“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 under water.”
The helicopter has since been recovered and towed to a pier. The cause of the crash is currently unknown.
Agencies contributed to this report