The 10-year-old American boy killed during a ride on the world's tallest waterslide was decapitated in the accident, a person familiar with the investigation says.
The person, who spoke on condition of anonymity, gave no other details about how Caleb Schwab died on Sunday on the raft ride at the Schlitterbahn WaterPark in Kansas City.
Authorities have yet to explain how it happened.
Two women who are not family members were in the raft at the time with the boy and were treated for facial injuries.
The boy's parents - Republican state Rep. Scott Schwab and his wife, Michele - have requested privacy and have not spoken publicly since the death. His funeral is scheduled for Friday.
A spokeswoman for the waterpark on Wednesday declined to discuss the circumstances of the boy's death on the ride called "Verruckt" - or German for "insane".
Verruckt featured multi-person rafts that make a 168 foot (51 metres) drop at speeds of up to 110kph, followed by a surge up a hump and a sharp descent to a finishing pool.
Riders, who must be at least 54 inches tall (137cm), were harnessed in with two nylon seatbelt-like straps - one that crosses the rider's lap, the other stretching diagonally like a car shoulder seatbelt.
Each strap is held in place by long Velcro-style straps, not by buckles. Riders also hang on to ropes inside the raft.
The park reopened on Wednesday except for the sprawling section that includes the waterslide, although its towering profile greeted visitors as soon as they drove through the entrance.
Pulling a cooler behind her, 42-year-old Sara Craig said she was looking forward to an afternoon of water fun on Wednesday with her 14-year-old son, Cale, and one of his 13-year-old friends.
But she said the visit came with a twinge of unease, given Sunday's tragedy.
"I feel guilty having fun when a family is hurting so badly," she said.
She said the family rode Verruckt twice in one day a couple of weeks ago. She remembered a short video they were required to watch, though she didn't recall that it including any caveats about peril.
Craig said that during her first trip down the ride with her son and one of his friends, her shoulder restraint came off, something she opted not to report to park workers.
"I didn't think much about it," she said. "You don't think you're gonna die."
So they rode it again, only to see the restraint on her son's friend also come loose by the time it was over.
Craig described the ride as "very, very rough," so much so that "when I got off, my head hurt".
The water park passed a private inspection in June that included Verruckt, according to a document released by a Kansas state agency.
Ken Martin, a Richmond, Virginia-based amusement park safety consultant, questioned whether the straps were appropriate.
In early tests, rafts carrying sandbags flew off the slide, prompting engineers to tear down half the ride and reconfigure some angles.
"I think ... they figured since stuff was flying out, we better do something to keep people from flying out," said Martin, who has not seen or tested the ride.
"I think we have a serious issue with the restraint system. Period."
