Christopher Kennedy invited a homeless stranger inside his home for a drink after the man stopped outside to ask for a cigarette.
But within hours Bradley Taylor had stabbed his host to death and tied a plastic bag over his head, before fleeing from the Geelong unit.
When he was interviewed by police days later, Taylor was wearing a T-shirt soaked in Mr Kennedy's blood.
Taylor, 37, appeared by video link from prison in Victoria's Supreme Court on Friday for a pre-sentence hearing, after pleading guilty to the murder.
He has been behind bars for more than two years, since his arrest for the June 2020 killing.
Taylor claims he was in a drug-induced psychosis when he killed Mr Kennedy, 49, at his Norlane home, defence barrister Jason Gullaci told the court.
A man who was at the unit before Mr Kennedy died said Taylor was angry, exerting physical ticks and fixated on finding a pedophile to fight that evening.
About 8pm on June 17, a neighbour heard Mr Kennedy shout "f*** off and don't come back" before Taylor stabbed him 11 times in the chest.
Taylor grabbed a plastic bag, filled with half-smoked cigarette butts, and tied it around Mr Kennedy's head.
He then went to the kitchen, turned on the gas stove, opened the oven and placed toilet rolls on the stove before fleeing the scene.
A nurse found Mr Kennedy dead the following day, his body covered by a doona.
Mr Gullaci said Taylor was listening to voices in his head when he fatally stabbed Mr Kennedy.
"It was a violent and brutal killing and there is no getting around that," he said.
"Some of the conduct he engages in post the physical assaults shows a level of disordered thought."
He said Taylor put a plastic bag over Mr Kennedy's head because he believed he could "catch his thoughts" and voices told him his victim was a pedophile.
"People told me the government was going to give me $300,000 to put these people away, and what he means by that is to kill them," Mr Gullaci said, referencing his client's admission to a psychologist.
"Mr Kennedy was not a pedophile, there is no suggestion ... that anything that he thought in the course of his psychosis was objectively accurate."
Taylor turned on the gas stove because he believed someone would smell it and find Mr Kennedy's body, he said.
He admitted Taylor would receive a significant jail term for the murder, but asked the court to allow him to serve a long period of his sentence on parole.
Prosecutor David Glynn described the murder as "savage" and entirely unprovoked by Mr Kennedy, who had graciously invited Taylor inside his home.
He argued Taylor should be handed a lengthy non-parole period.
Mr Kennedy's sister said his death had changed her life and she continued to be tormented by the killing.
"I keep thinking, how could anyone do this to a person, a stranger he just met," she said, in a statement read to court.
"The only thing that gives me any comfort is he is locked up behind bars and cannot do this to anyone else again."
Justice Lex Lasry will hand down Taylor's sentence next week.