Victims’ families have given moving testimonies of the devastating effects of the home insulation program on their lives.

The father of one victim in a botched home insulation program took just seconds, after his son’s death, to learn online that people in New Zealand had been killed by the same combination of foil insulation, staples and electricity.

That moment was the start of a long battle for the truth that, nearly five years later, led to Kevin Fuller and the families of three other victims testifying to its devastating impact on their lives.

Mr Fuller’s son Matthew, 25, was electrocuted as he put insulation into a roof as part of the disastrous stimulus program in 2009.

“I thought, hang on, if I can find that in 30 seconds, why can’t the Australian government, why didn’t the Australian government know that beforehand?” he said at the royal commission on Friday.

In an extraordinary testimony, Mr Fuller listed negligence and disregard he had encountered investigating Matthew’s death and trying to stop more.

Mr Fuller attempted to raise the alarm about the Home Insulation Program (HIP), including writing letters of warning to then-environment minister Peter Garrett and prime minister Kevin Rudd.

He said he felt guilty for not having achieved more when Rueben Barnes was killed a month after Matthew, followed by Marcus Wilson and Mitchell Sweeney before the program was halted.

“As just a father or just an Australian I expected the system would get off its arse, go and sort, go and find out, go and change things and make stuff happen. Nobody did,” he said.

Rueben Barnes’ older sister, Sunny, wept as she gave evidence at the commission, describing the impact the 16-year-old’s death had on her family, coming seven months after the death of their mother.

“Being that we were such a close-knit family and all lived at home it had such a devastating effect on our whole family,” Ms Barnes said.

The 27-year-old said she and her siblings struggled with depression and her relationship with her father was destroyed.

“I don’t like to say what we have now isn’t amazing but it’s very different,” she said.

The commission also heard from the father of Mitchell Sweeney on Thursday, with Mr Sweeney fighting back tears and saying no family should have to suffer as the victims’ families had.

“We love you very much, Mitchell and we will never stop missing you,” he said.

Mr Fuller criticised former prime minister Kevin Rudd for his behaviour in a meeting, saying Mr Rudd had disgraced himself with a rushed, uncaring approach.

Mr Fuller also savaged politicians and public servants who had told the commission they could not recall certain events or information.

“I know they would prefer to look stupid than guilty but that’s not what we need them to do when they come to these places, so there needs to be some ethics,” he said.

“When people go `I can’t recall’, `I can’t remember’, Christine and I have the opposite problem: we will never be able to forget what the HIP did to us – needlessly killing our own son Matthew.

“But almost as bad, too many of the people involved in that seemed not to care too much that people were killed in their program.”