As Benjamin Mihan waited in line for Dreamworld's Thunder River Rapids ride, he watched four adults and two kids float by in a raft, smiling and wet.
"They looked happy and soaked with water, you know, enjoying the moment," the father of two told the Herald.
Ahead of the group, an empty six-seater raft had become stuck in a dip - where a conveyor belt ended and looped underwater, and people could get off the ride.
The 28-year-old pilot thought perhaps the two boats would bump together, that one would push the other away, or they would both just stop.
"But within a few seconds it was just a tragedy."
Mihan lives "just around the corner" from Dreamworld.
With his Kiwi wife and their 2 and 4-year-old kids, they'd headed to the park for the afternoon, using their season pass.
"About 2.15pm I walked back towards the River Rapids to where you line up. I saw the family enter the conveyor belt."
Earlier in the day, when he walked past the ride, Mihan noticed the water level was lower than normal.
And as he watched the happy group move along the conveyor belt, the thought struck him again.
"It was like there wasn't enough water - as they were coming off the conveyor belt they hit the unoccupied tube in front - it was like it was stuck because there wasn't enough water to keep pushing it forward."
The rafts collided and the two families' one flipped upwards and rotated slightly to the left.
The two children, Ebony Goodchild and Kieran Low, were ejected clear of the water.
The men - Luke Dorsett and Roozi Araghi - went under the conveyor belt.
The women, Kate Goodchild and Cindy Low, were thrown into the water.
"The men stood no chance . . . That conveyor belt, it was moving quite quickly, it just ripped their chair apart," Mihan said.
He watched in horror as the men were pulled under the water.
"It was just awful. Maybe if the water level was a bit higher they would have stood a chance.
"It all happened so quickly, I don't think human intervention or an emergency stop button would have done anything.
"It was a horrific scene. I remember the dear little girl was screaming hysterically, she witnessed it . . . The father was trying to save his wife and she died in his arms," he said.
"There were so many people trying to help. But there was no way the men could have been saved."
Mihan recalls an ambulance officer describing the injuries as being "incompatible with life."
"That's the description they used. I think the men's deaths would have been quite quick."
In the following days sleep hasn't come easily to Mihan. He has returned to the park to lay flowers. "I just stood there. To pay my respects."
He has spoken to police and seen a counsellor - who suggested sharing his story may help him gain some kind of closure.
He is particularly disturbed by accounts of the incident placing blame on others - including an 18-year-old staffer alleged to have been manning an emergency stop lever by some media.
The incident took place so rapidly, nothing could have stopped it, he said.
"It was literally the last seconds before them getting off the ride."