The man who bashed a protective services officer with a hammer before stealing his gun and taking his own life had been acting "peculiarly" at Parliament House earlier that day.
As it emerged there was no CCTV footage of the assault, police said the man - now known to be a 30-year-old from Chadstone - had asked PSO James Vongvixay for directions shortly before hitting him in the head with a hammer.
On Wednesday morning, Mr Vongvixay was recovering in hospital from surgery to mend a fractured skull. He is in his 40s and has seven years' experience as a PSO.
Mr Vongvixay underwent surgery overnight and remains in a serious but stable condition. He is now conscious and has spoken to investigators.
It is believed Mr Vongvixay was hit several times on the head with a hammer shortly before 8.30pm on Tuesday, as he was engaged in a regular patrol outside Parliament House in Spring Street. He was knocked unconscious in the assault and his semi-automatic pistol stolen.
Police said there was a brief verbal exchange before the situation turned violent. Six minutes later, as the assailant fled through Fitzroy Gardens towards the MCG, he is believed to have shot himself.
Inspector John Potter said the man had been noticed outside Parliament House about 2.30pm by a woman who said he had behaved peculiarly.
She told a PSO at Parliament - a different officer to the one assaulted later in the day - about the man.
Mr Potter said the man then left the area, but it was unclear if he had been told to do so by the PSO.
Police said later on Wednesday that the woman had now come forward to speak to them.
The motive for the crime remained a mystery, but police would investigate whether being spoken to by a PSO earlier in the day had triggered the vicious assault.
"We don't know. We just don't know," Mr Potter said of the reasons for the crime.
"We're convinced this man was acting alone and obviously had some problems in his life."
Assistant Commissioner Andrew Crisp said the incident could have been far worse.
He called PSOs "unsung heroes" and said the injured officer had no warning he was going to be attacked when speaking to the man.
"There was nothing in that conversation to indicate what would happen next," Mr Crisp said.
"This is a terrible situation on the streets of Melbourne and it goes without saying there was the potential for this to go horribly wrong."
Mr Crisp said he was not concerned that the incident was not captured on CCTV and could not rule out a change to security arrangements at Parliament House. Three PSOs generally patrol the building, with two conducting individual foot patrols and another in a control room.
Mr Potter said it was unclear how many shots had been fired by the man, and what he had been doing between being sighted at Parliament earlier in the day and returning that evening. The earlier interaction with a PSO was captured on CCTV.
He would not comment on how the man was known to police, but said that history would form part of the investigation.
On Tuesday night, his body was lying on a reserve near train lines at the junction of Charles Street and Wellington Parade South.
The homicide squad is heading the investigation with oversight from the Victoria Police Ethical Standards Department and the Office of Police Integrity.
Parliament was sitting when the attack happened and additional police were called to the scene in an attempt to secure the site. Police cordoned off Wellington Parade South from Jolimont Terrace to Jolimont Road. Premier Ted Baillieu and other MPs were warned not to leave Parliament House.
A taxi driver who witnessed the incident told Fairfax Media he heard a voice yelling "he's got a gun, he's got a gun," and then saw the man run down the street.
Another witness, Rebecca Camilleri, said she had emerged from an event inside Parliament House just after the initial assault.
"We heard a half-moan, half-scream and as we walked down the steps we saw a guy lying there on the ground," she said. "You could see blood everywhere and there was a hammer next to him."
Protective Services Officers have similar powers to police and are armed, a decision that has angered some critics.
The officers have long been a fixture outside Parliament House but their use was only extended to Melbourne's train stations in February of this year.
The incident will raise questions about security at Parliament House with some witnesses describing a scene of confusion in the immediate aftermath.
Police Association Secretary Greg Davies said he was sick of PSOs being used as a political football.
He said he was comfortable with the number of officers rostered at Parliament House and the capabilities of PSOs who worked there.
‘‘If you want James Bond on the steps of Parliament House, give him a call. I believe he’s in between movies,’’ Senior Sergeant Davies said.
‘‘This is the first incident of this sort of crime in living memory.’’
Mr Baillieu and Deputy Premier Peter Ryan said in a statement on Tuesday night that police would conduct a thorough investigation.
On Wednesday morning, Mr Baillieu said he was generally happy about security arrangements at Parliament House.
But he said the construction site on the steps of Parliament House had created issues.
‘‘(It) has changed the line of vision around the front steps of parliament and I think there is an opportunity for a review of that.’’
He said there would be no changes to the way PSOs operated in light of the incident and there was no doubt they needed guns.
‘‘They need to be appropriately serviced and provided with all the equipment they need and that’s certainly the view of Victoria Police.’’
Speaker Ken Smith told Parliament that ‘‘James’’ was in a serious but stable condition and had been talking to his friends and family this morning.
‘‘We can only wish him well and hope that his recovery is quick and that he can be back with his family, certainly before Christmas.’’
Anyone who thinks they may have seen the man in the Spring Street area on Wednesday is urged to contact police.
The man is described as being 185 to 187 centimetres tall, with a solid build olive skin.
He was wearing dark-grey cargo shorts, a light-grey coloured T-shirt, black Adidas runners, a light-brown peak cap and a light-blue backpack.
With John Silvester
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