The last conversation Deborah McKenner recalls having with her father John McKenner was "basically me pleading with him to get better and be okay", after he'd become increasingly unstable.
"This was the day before my dad shot and killed my mum and himself," Ms McKenner told the hearing into veteran suicides on Thursday.
Ms McKenner was 11 in 1980 when she intervened as her father tried to strangle her mother with a hairdryer cord.
He attempted suicide days later and was discharged from the army about seven months after.
She witnessed her father strangling her mother again in 1982 and realised her mother's life was in "extreme danger" after he broke into their home, holding what she believes is "the gun that killed him".
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 a 'battered housewife'".
It was "wrong on so many levels" and the children were "suddenly put in an orphanage" eight days after the murder-suicide.
Ms McKenner says she suffered "many forms of abuse" while the ADF "did nothing to help me or my brothers".
"I've lived for this day where I can finally talk and be heard about my family and how six people's lives were destroyed by the Australian Defence Force's lack of care."
She says there needs to be proper recognition of how the Vietnam conflict impacted on servicemen and their families, noting she has "met many other military children and spouses battling similar demons with no help to be seen anywhere".
Commissioner Peggy Brown says Ms McKenner's testimony was a "very poignant reminder about how important it is to think about families and how long the trauma and grief goes on".
Earlier on Thursday, Australia's first Veteran Family Advocate Commissioner Gwen Cherne told the hearing any response to the scourge of veteran suicide will fail if it doesn't support families experiencing violence.
She is the daughter, widow and mother of veterans and her husband Peter took his own life in 2017.
Three days before he took his life, amid fears he was being pushed out of the ADF following a stroke he suffered serving in Iraq in 2016, Ms Cherne left their home with their children following what would be the last of a number of violent incidents that began months after they married in 2010.
Prior to the stroke, her husband told command that "he was not okay" and was told "to either delegate better or suck it up essentially".
High-ranking defence members such as commanding officers should be connected and engaging with families of soldiers in their unit, with "a constant flow of access and information and trust building", Ms Cherne says.
"If you can create that, even with a small group of families who then have access to other families, you're able to have the pulse on the men and women in your unit.
"You're able to understand what's going on in their families and then de-escalate."
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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