Stephen Peter O'Brien's son Scott had never moved out of home and his erratic behaviour had led to a "significant history" of family violence towards his parents which went unreported, the Victorian Coroners Court was told.
On January 6, 2023, Stephen spoke to his sister for the final time and told her he did not want to go home because he was concerned about Scott's mental health.
He said Scott thought Stephen was a federal police officer and whenever he went home his son accused him of spying.
Stephen called a farm owner and said he intended to go to work on January 9, but he never made it there.
The next day Stephen's daughter requested a welfare check, and police found him dead, covered in blood, on the floor of his Wyndham Vale home.
An autopsy revealed he had died from blunt force injury to his head, due to multiple blows with an implement.
Scott was arrested on January 11 and charged with his father's murder, but was found not guilty by reason of mental impairment in April 2024.
State Coroner John Cain, in findings released on Wednesday, said Stephen had spent years trying to manage Scott's behaviour and violence to keep himself and his late wife Elizabeth safe.
Scott had assaulted Stephen several times, leading to bruising, black eyes and at least one hospitalisation for a facial fracture, the coroner said.
Stephen had told others he was stressed and frightened by Scott's behaviour and often booked accommodation to have a break.
Scott would shout at his father while he was on the phone and threaten anyone who came to visit their home, and reportedly had a diagnosis of schizophrenia but did not take medication or receive treatment as he presented as "functioning OK", the coroner said.
Friends had offered Stephen free rent and work in Bendigo, after his wife died, but he declined "because of Scott".
Judge Cain said Stephen's case was "sadly" one of several before the court where an adult child with undiagnosed or untreated mental health issues had assaulted or killed an older parent.
He said many barriers had prevented Stephen from getting help, including fear of negative consequences for Scott, lack of knowledge about resources available to him, and that he may not have recognised it as elder abuse.
He urged the Victorian government to raise awareness about elder abuse through targeted campaigns and community education, to empower them to understand what it is and to report it.
Stephen's situation was not unique, Judge Cain said as he pointed to Mind Australia data that half of the nation's mental health carers' support needs were not being met, and 35 per cent did not know that support was available.
"Stephen was a 'hidden' carer in that he did not identify as a mental health carer and was not receiving benefits to care for his son," he said.
The coroner said it was "critical" the state government work to identify hidden carers and support them through mechanisms such as a carer assessment tool via GPs, health centres and schools.
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