The day before the killing on May 24 last year, Duhovic was at home in Thornbury shaking off the effects of a flight home from Vietnam. Mr Hogan meanwhile was preparing for a marriage celebrant to visit his Bacchus Marsh home that night, to discuss his coming wedding.

His fiancee, a Chinese national more than 20 years younger than Mr Hogan, had moved in less than two months earlier and things were happening fast, though their relationship was said to be volatile.

Tragically for Mr Hogan, a 48-year-old father-of-five, things moved even faster from about 5pm on May 23, when the woman sent a text message to Duhovic, whom she had lived with months earlier after meeting online.

Just 15 hours after that initial text, Duhovic blasted Mr Hogan from point-blank range.

The Supreme Court heard on Friday, that Duhovic had been convinced by Mr Hogan's fiancee that he was a violent and dangerous man.

Duhovic, 34, pleaded guilty to murder and one count of recklessly causing injury, the second charge related to Peter Hughes, Mr Hogan's housemate, who had been sitting in his friend's van when the gunman walked to the driver's window and fired. Mr Hogan was about to drive Mr Hughes to the train station.

Mr Hughes only had time to say "Paul, gun", prosecutor Jeremy McWilliams told the court, before the shot was fired. Mr Hughes was hit in the hand and ran from the vehicle.

The night before the murder, it was said to have been plotted in 216 telephone communications shared between Duhovic and the fiancee.

"I want to kill it," she said in a text message to Duhovic in reference to Mr Hogan.

Duhovic told her not to talk "silly" things, but over the hours became convinced she was in physical danger and that he needed to save her from Mr Hogan.

Early the next morning, Mr McWilliams said, the woman told Duhovic she had been beaten and raped by Mr Hogan, and that Duhovic's own daughter was at risk. She gave a physical description of Mr Hogan and his van, and said he had to be killed.

Duhovic drove to Bacchus Marsh with the intention of getting her out, but also had a shotgun. The court heard he was a Buddhist, did not use drugs or abuse alcohol and had no criminal convictions, but had access to firearms at a rural property where his family worked.

When Duhovic turned into Mr Hogan's street, he saw the van reversing over boxes of his fiancee's possessions.

It was at this point, defence counsel Philip Dunn, QC, told the court, that Duhovic became convinced of the allegations of violence the woman had made about Mr Hogan.

But those allegations were, Mr Dunn said, "regrettably untrue".

"He has made a dreadful, dreadful error of judgment," he said of his client.

Duhovic, Mr Dunn said, had been completely misled by the woman, and would forever ask himself: "Why on Earth did I do this? Why on Earth did I listen to what I was told by someone I didn't know?"

"He stupidly fell in with it," Mr Dunn said.

"He will have to carry the error of judgment and stupidity for the rest of his life."

After shooting Mr Hogan, Duhovic dutifully collected the woman's belongings and drove her to hospital, still believing she had been raped. Police arrested the pair the next day.

Duhovic was a teenager when he suffered a brain injury in a motorcycle crash and now lacked the ability to think rationally, Mr Dunn said.

His father Stephen Duhovic told the court his son's thinking was much slower after the motorcycle accident, and that he had always been protective and willing to help those closest to him.

He said of the woman, that from the day he met her, he had never liked her.

"She's a user and a manipulator, I saw that from day one," he said.

The woman, 27, who is charged with murder and is awaiting trial, befriended six men online when she arrived in Australia.

Duhovic had been the "third cab off the rank" on May 23 last year, Mr Dunn said. He said she had earlier spoken of killing Mr Hogan with two other men.

Mr Hogan's mother, Valda, in a victim impact statement likened the news of her son's death - via the late-morning television news - to being shot with a "canon through the chest".

"I live in the past or in the future because living in the present is too painful," she said.

Duhovic showed no emotion in court, but has written a letter of apology to his victim's children.

"He is very remorseful," Stephen Duhovic said of his son. "I haven't asked the question why (he did it)."

Justice Jane Dixon will sentence at a later date.