The helicopter carrying coal billionaire Chris Cline began spinning before it plunged into the ocean near the Bahamas and killed everyone on board, federal authorities said Tuesday.

The National Transportation Safety Board's preliminary report details the July 4 accident and its aftermath but doesn't include a cause.

Cline, his daughter Kameron and three of her friends died along with a pilot and copilot in the crash off Cline's private Big Grand Cay island.

Scroll down for video

Chris Cline, his daughter Kameron and three of her friends died along with a pilot and copilot in the crash off Cline's private Big Grand Cay island on July 4

The aircraft was leaving the island to take two passengers to Florida for medical treatment, the NTSB said . Cline had been trying to get his daughter Kameron to the hospital

The aircraft was leaving the island to take two passengers to Florida for medical treatment, the NTSB said. Cline had been trying to get his daughter Kameron to the hospital.

A witness saw the helicopter rotate to the left three to four times, followed by a whooshing noises and the sound of an impact just a minute after the flight took off, the report said.

'The witness reported what he had heard to the "caregiver" of Big Grand Cay,' the reports states.

'The witness went out on his boat about 0205 and used spotlights to search the area where he thought the helicopter had crashed but was unable to locate it.'

The helicopter was found upside-down in about 16 feet (5 meters) of water with its rotor blades separated. Investigators brought it to a secure site in the United States.

The helicopter was found upside-down in about 16 feet (5 meters) of water with its rotor blades separated. Investigators brought it to a secure site in the United States

'All five main rotor blades were separated but recovered,' the release states. 'The tail rotor assembly, which was also separated was subsequently recovered.

'All four tail rotor blades were separated, and one tail rotor blade was not recovered. The recovered wreckage was retained for further examination, to include examination of the airframe, engines, flight controls, seats and restraints.'

Flight and data recorders have been recovered and shipped to the NTSB in Washington for analysis, the Bahamas Air Accident Investigation Department has said.

Cline's death led to eulogies from coal industry leaders, government officials and academics, who described him as a visionary and generous philanthropist.

He accumulated a $1.8 billion fortune from a career that he began years ago as a coal miner in southern West Virginia. Cline bought Big Grand Cay in 2014.

Kameron had suffered a medical emergency and Cline was eager to seek treatment for her, according to family friends.

Delaney Wykle (left), Jill Clarke (center) and Brittney Searson (right) also died in the crash. They had all recently graduated and were friends of Kameron

Geoff Painter, left, was flying the helicopter. He ran Cloud 9 Aviations with David Jude, right, who was also on board

Three of her friends, who had been in the Bahamas on the Clines' private island with her, were on board along with David Jude and pilot Geoff Painter, the owners of a Palm Beach helicopter service who sometimes flew privately for the family.

Cline would have turned 61 the day after the crash.

Friends say he and the group were on his private island to celebrate a birthday but it is unclear if it was his or someone else's in the group.

Kameron, one of his four children, had joined him along with three of her friends; Delaney Wykle, 22, Brittney Searson and Jillian Clark.

The full investigation into the crash could take up to two years, a NTSB spokesman said earlier this month.