NEW YORK -- Federal investigators are trying to zero in on what caused a tourist helicopter to fall from the sky over New York's East River Sunday evening. Five passengers who booked the flight to take pictures were killed. The chopper's pilot managed to escape.

Crews pulled the battered helicopter out of the water Monday. Divers were forced to cut the passengers out of their safety harnesses.

One victim, Trevor Cadigan, shot video as the flight took off, showing the harnesses the passengers wore. The metal ring on the back tethered them to the helicopter during the open-door flight.

Pilot Richard Vance told investigators a tether from a harness worn by one of the five passengers wrapped around the fuel shutoff lever and "accidentally" cut off the fuel supply causing the chopper's engine to fail Sunday night.

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

Eric Adams was with the same group on another helicopter Sunday night. He took several pictures of the doomed chopper. Asked whether crew members showed him hot to get out of the harness in a hurry, Adams responded, "Not as well as they should have."

He said "it is very unlikely" he could have freed himself if he was upside down in the dark water. "I'd like to think that I could have but accidents happen fast," Adams said.

CBS News went for a similar open-door helicopter ride over Manhattan on Monday.

The harness, along with a seatbelt, is designed to keep passengers inside the helicopter. The chopper was about 1,300 feet up above the Hudson River, and if the engine shut down at that point, the helicopter would have been in the water in four seconds.

Peter Zanlunghi has been flying helicopters for more than three decades.

"I imagine it would be fairly disorienting to try to get all this stuff off in an emergency when you are upside down and under water?" we asked.

"It would definitely be disorienting. Your body is not in its comfort zone," Zanlunghi said.

Liberty Helicopters operated the flight that crashed. It said it is focused on supporting the families affected by the tragic accident and is fully cooperating with the Federal Aviation Administration (FAA) and National Transportation Safety Board (NTSB).

The NTSB has yet to speak with the pilot but he did talk to law enforcement Monday night. It's not surprising he got out -- he would be the most familiar with releasing a seatbelt or a harness and he was right next to an exit. But what happened after the crash will be a focus of the investigation.