The former youth recreation worker was horrified security had not closed off the area and children under 10 years were watching the boy threaten to jump. One asked Mr Gunn if the boy would come to recreation tomorrow or have killed himself by then.

Mr Gunn is a Canberra-based whistleblower who wrote some of the 2000 incident reports detailing trauma suffered at Nauru, most recently evidenced in Guardian Australia's release on Wednesday.

He and fellow Canberran Jane, who chose not to use her last name, are two of the 26 former Save the Children workers who wrote an open letter in response to the leaked files which they say reflected their daily experiences.

The pair are pleading Australians to listen to their firsthand experiences which expose a pattern of systemic abuse and neglect of children who sought safety from them, after Immigration Minister Peter Dutton responded to the leak by accusing asylum seekers and refugees of making false abuse allegations and self-immolating to get to Australia.

Mr Gunn, who wrote one file which gave a harrowing account of a Nauru guard bashing a toddler at the detention camp, said workers were so familiar with the mental and physical deterioration of children in detention that that they could foresee their breaking points – all while powerless to stop it.

"There was a growing frustration as you could see children you were working with in a downward spiral yet you did not have the ability to stop that spiral so all you could hope for was slowing that process down," he said.

"There was an inevitable outcome and you knew what was going to happen. You used to always look at their eighth month [in detention]. Once they hit that mark that was when things went down, you would get self-harm, you would get the trauma really establish itself within the person."

Despite having a wealth of experience working on the frontline of child protection and youth work before working on Nauru, Mr Gunn and Jane said they could not have prepared themselves for the horror they witnessed on the tiny Pacific island.

"It cannot prepare you for engineered destruction of family units, or children, and in a place where you are so powerless," Mr Gunn said.

Fighting back tears, Jane said she developed a deep respect for the refugees she worked with.

"It has had a huge impact on all of us [save the children workers]," she said.

"But it was the things that they [the refugees] have endured to get where they are and sometimes it is actually their strength, knowing how much more they have endured than we have, that gets you through."

While human rights groups have made the case for the child abuse royal commission to investigate the endemic sexual violence, abuse and self-harm at the Nauru facility, Prime Minister Malcolm Turnbull brushed aside the calls, saying the documents were just allegations, not findings.

But Mr Gunn said previous inquiries, including those done by the Australian Human Rights Commission and the Senate, already proved the systematic abuse and the leak was the tip of the iceberg.

"What is absent in these reports are the childhoods lost, the families broken and the ongoing effects that this abuse leaves on the lives of these innocent people," he said.

He called for all refugees on Nauru to be resettled in developed countries where they can be rehabilitated and supported in their road to recovery.

And despite facing up to two years in prison for speaking out against conditions on Nauru under immigration laws, he vowed to keep fighting for their freedom.

"If I was placed within prison I would be placed in better conditions with access to better services than those children," he said.

"So how could I justify keeping silent?"

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