BECKLEY, W. Va.  – The helicopter carrying billionaire philanthropist Chris Cline, his daughter and five others slammed into the ocean off Cline’s private island in the Bahamas one minute after liftoff on July Fourth. All seven aboard died.

The details of the tragedy were contained in the National Transportation Safety Board’s preliminary inquiry report released Wednesday. A full investigation into what caused the crash could take up to two years, said Eric Weiss, a spokesman for the agency.

The report said the helicopter, responding to a medical emergency, lifted off shortly before 2 a.m., according to witnesses, and promptly dropped from 50 feet, slamming into the Atlantic 1.2 miles from its departure point.

Cline family members called authorities at 2:53 p.m. to report the helicopter had not arrived at its Fort Launderdale-Hollywood International Airport destination, prompting the Federal Aviation Administration to issue an overdue flight alert at 3:21 p.m.

The NTSB said local searchers in boats found the 17-seat Agusta Westland AW-1339 inverted in 16-feet of water between 4 p.m. and 5 p.m.

Bahamian authorities recovered the copter. They said the tailboom had broken into pieces, separated from the fuselage. The five main rotor blades and four tail rotor blades were also detached from the craft. Those aboard the copter were found wearing seat belts.

The NTSB report quoted one witness about 1.6 miles from the accident site as seeing the helicopter lift off, then blue and white lights spinning to the left at a rate of 1 to 2 seconds between rotations while descending. He estimated the craft rotated to the left  three to four times before he heard a “whoosh whoosh whoosh” sound and lost sight of it – and then heard it crash into the ocean.

The NTSB said the witness reported the sighting to the “caregiver”of Big Grand Cay and took off in his boat to search for the helicopter but couldn’t find it.

The NTSB said the copter left from the West Palm Beach, Florida, Airport around 1 a.m. and landed at Big Grand Cay between 1:30 and 1:45 a.m. to transport the Cline party to Fort Launderdale. The pilot kept the engines running while the passengers boarded.

Meterologists reported weather was not a factor in the crash, noting it was a dark night but no clouds present. The copter’s flight plan indicated the pilot would be using instruments instead of sight navigation because of the nighttime.

In addition to Cline and his 22-year-old daughter Kameron, crash victims included Brittney Layne Searson, 21, Palm Beach Gardens, Florida; Jillian Nicole Clark, 22, of Louisiana; Delaney Lee Wykle, 22, Beckley, West Virginia; Geoffrey Lee Painter, 52, Barnstaple, United Kingdom, and David Jude, 56, of Wyoming County, West Virginia.

Kameron, Layne and Jillian were sorority sisters at Louisiana State University in Baton Rouge. The NTSB report did not identify the helicopter’s pilot or co-pilot.

A native of Beckley,West Virginia, Cline had arranged the helicopter flight because his daughter had fallen ill, according to family members. The NSTB report said one other passenger also needed medical attention but it did not identify the person.

Cline, who would have turned 61 the day after the crash, made his fortune in the coal industry, starting as an underground miner in West Virginia and rising through the ranks to start an energy company that he built into a powerhouse and later sold. Forbes magazine estimated his net worth at $1.8 billion. He was a generous contributor to the University of West Virginia and also to philanthropic causes in his home state and elsewhere.

He owned a oceanfront mansion in Palm Beach, Florida, and a compound of homes and cottages on Big Grand Cay, a small island that’s part of an archipelago of Bahamin islands.

The Beckley, West Virgnia, Register-Herald provided details for this story.