Constable Dean Wotherspoon also conceded Tasmania Police should have done better in relation to the mother of one victim being prevented from accessing the oval in Devonport.
Addison Stewart, Chace Harrison, Jye Sheehan, Jalailah Jayne-Maree Jones, Peter Dodt and Zane Mellor died when a freak wind gust hit Hillcrest Primary School in December 2021.
The castle and other inflatable equipment had been set up for end-of-year celebrations.
The inquest has been told only half of the castle's eight anchorage points had pegs in them, while an inflatable Zorb-ball barrier had pegs in six of 32 points.
Const Wotherspoon, who has decades of experience in forensic investigations and was one of the first officers to the scene, was asked about his opinion of the tethering.
"There was insufficient anchorage on the castle and the Zorb barrier," he said on Wednesday.
There were unused pegs and star pickets, which are used to secure items, "readily available" in the back of a trailer belonging to castle operator Taz-Zorb, he said.
Const Wotherspoon said the absence of a clear chain-of-command line for police hampered operations and their ability to secure the scene.
A breakdown in communications at the scene was highlighted by Georgie Burt, the mother of Zane, being prevented from accessing the oval while other families were allowed, he said.
"Who made the decision that one family could go in and another family couldn't?," Const Wotherspoon said.
"It is obvious that we can and should have done better."
Ms Burt previously told the inquest she was told Zane had been taken to a nearby hospital before later finding out he had died on the oval.
There should have been a clear point where police paused and came up with a plan to secure the oval properly, Const Wotherspoon said.
He was moved to tears when describing the "profound" impact of the tragedy on him and the police force, given the children were celebrating the next chapter of their lives.
"It's a rule of nature that you're not meant to outlive your children," he said.
"If not directly responsible for ending some (police) careers, it has hastened it.
"People did their utmost to save lives."
The inquest will continue on Friday with evidence from Tasmania Police assistant commissioner Adrian Bodnar, before further hearings in November and February.
In 2025, Taz-Zorb operator Rosemary Gamble was found not guilty of criminal workplace safety breaches releated to the incident.
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