NEW YORK -- The pilot of a helicopter that crashed into New York City's East River on Sunday night has told investigators that a strap from a passenger's harness inadvertently shut off the helicopter's engine, sending it plunging into the water. Five passengers were unable to free themselves and were killed in the crash. The New York City Police Department identified the victims on Monday as Daniel Thompson, 34; Tristian Hill, 29; Trevor Cadigan, 26; Brian McDaniel, 26; and Carla Vallejos Blanco, 29.

An Instagram video posted by Cadigan to Instagram shows him and other passengers on the helicopter as it was taking off, smiling and flashing a thumbs-up. Cadigan was a video journalist who had moved to New York just months ago, according to the New York Post. The helicopter was being used for a photo shoot.

Sources familiar with the investigation identified the pilot as 33-year-old Richard Vance of Danbury, Connecticut. Vance was the only survivor of the crash, and provided a statement to investigators, a portion of which was reviewed by CBS News.

Get Breaking News Delivered to Your Inbox

Vance told police he "observed ... a tether from a front passenger's harness wrapped around the fuel shut off lever, which had accidentally cut off fuel supply to the engine resulting in engine failure," according to his statement, provided by a source familiar with the investigation. "At that point, the engine could not be restarted and the aircraft descended into the water."

A crane pulls a helicopter out of the East River in New York City after it crashed Sun., March 11, 2018. CBS New York

The Eurocopter AS350 helicopter went down about 7 p.m. in the water near New York's mayoral residence. All five passengers died, but the pilot was able to free himself and survived.

As the aircraft foundered, the pilot was heard on an emergency radio transmission calling: "Mayday, mayday, mayday."

"East River -- engine failure," he added. The pilot was rescued by a tugboat, but emergency divers had to remove the passengers on the charter helicopter from tight safety harnesses while they were upside down, New York Fire Commissioner Daniel Nigro said.

"It took awhile for the divers to get these people out. They worked very quickly, as fast as they could," Nigro said. "It was a great tragedy that we had here."

The National Transportation Safety Board dispatched investigators Monday. Officials held a press conference Monday afternoon to say they will be investigating the maintenance record of the helicopter and the events leading up to Sunday's crash. They urged anyone with pictures, video or information to contact them.

NTSB also said that they will be interested in talking with the pilot, NTSB member Bella Dinh-Zarr said Monday.

"We will be asking him to be interviewed and we hope he'll comply because obviously our only purpose here is to ensure this type of accident doesn't happen again," NTSB official says https://t.co/UM2soqxIEr pic.twitter.com/PgZ6Wi8MVM — CBS News (@CBSNews) March 12, 2018

Dinh-Zarr said the helicopter's floats inflated, but investigators will look at whether they deployed properly.

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.

Witnesses on a nearby waterfront esplanade said the helicopter was flying noisily, then suddenly dropped and quickly submerged. But the pilot appeared on the surface, holding onto a flotation device as a tugboat and then police boats approached.