The 33-year-old woman from Schaumburg, Illinois, had already died by the time they arrived at the nearby Sunset Grill Marina, authorities said. Her 10-year-old son and 9-year-old nephew were taken to hospitals for treatment.

John Callion, a fishing guide, raced around Pigeon Key to reach them, his fiancée, Kasey Platt, told WPLG.

“He was pretty frantic on the call. He said, ‘Call 911 right away,’” Platt told the television station.

Callion told the Miami Herald that the Memorial Day storm developed suddenly.

“It was pretty much flat calm, but you could see the storm coming. All of the sudden, the temperature dropped by 10 degrees and the wind started blowing like crazy,” Callion said.

The captain on the boat pulling the parasail “cut a line tethered to the three victims” because the parasail was “pegging,” or dragging the boat, according to a Florida Fish and Wildlife Conservation Commission report released Tuesday night.

The woman and children were then dragged “through and across the surface of the water” by the inflated parasail until they collided with the Old Seven Mile Bridge, the agency’s report said.

Callion found the 10-year-old boy battered but awake. The 9-year-old boy was unconscious and wrapped in the parasail’s lines.

“It was pretty much the worst thing you could imagine,” he said. “It was real bad.”

The Coast Guard and the state’s wildlife agency are investigating.

“Our condolences are with the family and loved ones of those affected by Monday’s accident,” said Capt. Jason Ingram, Coast Guard Sector Key West commander. “This was a tragedy for a family seeking to enjoy their visit to the Florida Keys.”