But the Vietnam veteran's increasing instability did not ease.
"This was the day before my dad shot and killed my mum and himself," Ms McKenner told a Royal Commission into Defence and Veteran Suicide on Thursday.
Ms McKenner was 11 in 1980 when she intervened as her father tried to strangle her mother. He attempted suicide days later and was discharged from the army about seven months after.
Her mother wasn't taken seriously when she reported violent incidents to the army and the police.
"Mum had an AVO, only mum never had black eyes ... mum was not (considered) a 'battered housewife'," she said.
The Australian Defence Force "did nothing" to support her father, protect her mother, or care for their children who were sent to an orphanage eight days after the deaths, she said.
There needs to be proper recognition of how the Vietnam conflict impacted servicemen and their families, Ms McKenner noted, adding she has "met many other military children and spouses battling similar demons with no help to be seen anywhere".
It was a common theme in the latest day of evidence of the ongoing commission, which was told veterans are not getting the support they need amid a surge in demand for assistance.
Consultancy firm McKinsey was approached by the Department of Veterans Affairs to advise what it could do about a backlog of claims.
"Demand was far greater than what anyone expected, and the capacity of the department was lower than what it needed to be," McKinsey partner Bruce Hunter told the commission hearing on Thursday.
McKinsey reported the department needed at least 130 more full-time staff just to deal with the inflow of new requests, which increased 48 per cent each year between 2019 and 2021.
"To actually diminish the backlog they need more than that," Mr Hunter told the hearing.
Australia's first Veteran Family Advocate Commissioner Gwen Cherne told the hearing any response to the scourge of veteran suicide will fail if families caught in a "trap" of violence aren't given assistance.
The one-time defence wife criticised "punitive measures" that served as structural impediments for serving soldiers to seek support.
There were also "institutionalised power imbalances" affecting families living in defence housing.
A no-tolerance policy for domestic violence in the ADF is not effective, with those experiencing violence fearing they'll exacerbate the situation by reporting the abuse and negatively affect their partner's careers, Ms Cherne said.
That's the reason she didn't report her husband's abuse, which began shortly after they married in 2010.
The last incident occurred three days before he took his own life in 2017, fearing he was being pushed out of the ADF after suffering a stroke while serving in Iraq.
Soldiers instead need to be trained to recognise and identify domestic and family abuse, including when they're the perpetrators, Ms Cherne says.
"We need to be looking at a rehabilitative process ... if they're not participating actively in that there needs to be accountability," Ms Cherne says.
It's "insane to me" that defence will "compel men and women to cut their hair to a certain millimetre ... but won't compel them to participate in mandatory training when you know domestic and family violence will have a negative impact ... and the likelihood of that cycle continuing is astronomical," she said.
The inquiry is taking evidence on urgent issues from those in the ADF community who have had suicidal ideation, and family members of those who have taken their lives.
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