As Greg Anderson left the Frankston accommodation house where he had been staying, he told fellow residents he would not be coming back.
Later a large knife was found missing from the house.
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Victoria's Police Chief Commissioner Ken Lay has said police came into contact with Luke's father in January and that there were outstanding warrants for Anderson to attend court dates.
It is believed the 54-year-old concealed the knife and other personal items in a bag he took with him on Wednesday, catching public transport and walking to Tyabb's recreation reserve.
It was there the mentally ill Anderson killed his son Luke Batty before being fatally shot by police.
As police were checking an accommodation house for clues, it emerged that Anderson's descent to homicidal madness was slow, painful and unchecked by authorities.
The unskilled but not unproductive worker once moved from job to job, chasing a pay packet rather than a career.
However, in the past few years the jobs dried up, partially due to his age but mostly due to his nature. He simply wasn't wanted. His marriage broke up and his remarkable wife, Rosie Batty, urged him to get help, but he refused to admit he had a mental illness.
Even though he was showing growing signs of violence he was still given formal access to Luke at the cricket. The reasoning was that nothing was likely to go wrong in public. After all, his erratic behaviour tended to moderate around the bubbly young boy.
''He adored his son,'' a source close to the family said. ''Luke was the only thing he cared for.''
The world was closing in on Anderson. He was unemployed and now unemployable.
He knew he would never be granted shared custody of his son or even allowed overnight visits. His car was unregistered, making it difficult to even get to cricket training to see Luke.
He knew his tenuous links to his son were fraying.
On Wednesday he took the train to Tyabb with the concealed knife. His plan, police believe, was to commit ''suicide by cop'' after killing Luke.
Initial investigations indicate he didn't kill his son as an act of revenge or out of murderous rage, but through the fog of his mental illness he saw it as the only possible release for both of them.
The savagery of the attack showed he was determined to kill the 11-year-old.
Anderson made no attempt to escape. He waited for the police, fought through the pain of the capsicum foam sprayed on him and then, still carrying the knife, ran at one officer screaming that he wanted to be killed. That policeman fired one shot that hit Anderson in the chest. He died in hospital about six hours later.
His plan, borne from madness, was now complete.
There were five warrants out for Anderson's arrest when he smashed his son with a cricket bat and then attacked him with a knife. But he was never looking at serious jail time. Such relatively minor offences usually result in immediate bail.
The police computer system - a 20-year disaster - failed to notify operational police that he was wanted, but this murder cannot be written off as a law-enforcement failure. The senseless death of someone so innocent has again raised the iceberg-deep issue of domestic violence.
But the real issue is our inability to deal with the mentally ill, and the problem is getting worse. It is a massive problem, so much so that all police are being retrained to deal with the deeply disturbed.
In 2009 police dealt with 4798 people so disturbed that they were taken to a mental health triage centre. In 2012 that number had jumped to 7901, which equates to one every 67 minutes.
In 2008 of almost 4000 incidents where force was used by or against police, around 15 per cent involved mentally ill offenders. Four years later that had jumped to 35 per cent.
Many of these people - at least two a week according to police figures - engineer incidents where they try to provoke police to shoot them.
In 2011 nearly half Victoria's 245 sieges involved a person with a psychiatric issue.
Homicide investigators say that in at least 20 per cent of murders the offenders have serious mental health problems.
The mentally ill are more likely to be victims or offenders of serious crimes.
And even now when police are called to a scene, they can check the suspect's criminal history but do not have access to mental health issues.
Recently retired Superintendent (training) Mick Williams says this means police are ''flying blind'' when they come in contact with someone having a psychotic episode. Police say that with the closure of many of Victoria's mental health institutions they have left them to deal with the problems on the street.
Many people with mental problems never come into contact with police and most who do return to the community after treatment.
But there are some whose demons have left them violent and uncontrollable.
Greg Anderson didn't snap. He slowly broke and followed a path of irrationality, depression, threats, violence, murder and finally, suicide by cop.
If he had been assessed, treated and possibly hospitalised when he first came to notice then maybe, just maybe, both he and his son would be alive.
For information and help regarding family violence visit Domestic Violence Victoria or in an emergency call police or the women's domestic violence crisis services on 1800 015 188.