At 132cm, the six-year-old was tall for his age and able to ride without an adult, but there was a rule that he couldn't ride unless he was with his older siblings.
When last ride was called on the final day of the Rye Easter Carnival in April 2017, he lined up with a younger friend.
For the first time, he was placed in the outside seat, meant for adults and bigger kids.
His smaller friend, who should have been riding with an adult, was seated beside him.
The ride started up and the pair slid into each other as it spun around.
Some witnesses say it was going faster than usual, others say it was the regular speed.
But everyone saw a small boy outside the Cha Cha car, holding on tight and looking frightened. Then he fell.
Eugene struck his head on part of the ride before landing on the ground beneath it.
His parents Tammy White and Stacey Mahauariki, who both worked for the ride operator Wittingslow Amusements, heard the noise and rushed to help.
Eugene was flown to hospital but could not be saved. He died after life support was turned off on April 21, 2017.
"Eugene was a small child enjoying a ride at a fair on an Easter long weekend like hundreds of other children," counsel assisting Rachel Ellyard told an inquest into his death on Monday.
"The Cha Cha is an example of many rides that are fun because they're a bit dangerous, or at least they feel dangerous."
But parents only let their child ride because although they feel like they're on the edge of danger, they're actually safe, she said.
Parents and riders expect the machinery is in good order, the ride is safe and its operators are well trained.
Those are all elements of the accident that claimed Eugene's life that will be examined by coroner Sarah Gebert over the next two weeks.
"The loss of such a young child, and particularly in the circumstances, is undoubtably devastating to his family, also to our community as a whole," she said.
"We collectively shudder at what has happened, and all look for answers as to why."
Eugene's father Stacey Mahauariki told the inquest he let his son ride alone, but only when he was the one operating the carnival ride.
He was strict with enforcing safety rules including height limits because small children would slide around, he said.
Properly installed seat belts could have prevented the tragedy, he said.
Wittingslow Amusements was charged by WorkSafe with failing to ensure people other than employees weren't exposed to health or safety risks, on the basis that the restraint system was not sufficient.
Those charges were withdrawn in early 2020.
Wittingslow Amusements' owner Michael Wittingslow and engineer Hamish Munro, who inspected the ride five months before Eugene's death, have both refused to give evidence even after the coroner offered them protection from self-incrimination.
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