The family of a missing Melbourne man fears he may have fallen victim to a violent crime at his home.
Brendon Farrell, 32, was last seen by a friend on May 31 at his home in Doveton, in the city's southeast.
He had been living in a rear bungalow for about a year, and police believe a "significant violent event" took place there on the day he suspiciously disappeared.
"We know that there were a number of persons present on that day," Detective Inspector Andrew Stamper told reporters on Thursday, as he launched a public appeal for information.
"Some of those persons we have spoken to; some of them we haven't. Some of them we know; some of them we don't."
Mr Farrell spent time in jail for a minor crime and had been taking ice for about nine years.
But his sister Simone Hellyer said he was starting to get his life back on track and was working on and off as a forklift driver.
"I thought he was doing a lot better in the last six months since I'd had my baby," Ms Hellyer said, describing him as her "rock".
The last time she saw him at her partner's birthday party on May 22, the motorbike enthusiast brought some Harley Davidson bibs for his niece.
His family reported him missing on June 2, with his mother Valery alarmed when he stopped his usual daily contact with her.
Checks of his bank accounts and phone later revealed neither had been used since May 31.
"We fear that the worst has happened," Ms Hellyer said as her mother wiped away tears.
"I hear my mum cry herself to sleep every single night. It's the hardest thing I've ever seen my mum go through."
She said it was unthinkable her brother would do a runner.
"He wouldn't be away from us this long. He wouldn't go this long without contacting us or seeing his niece," Ms Hellyer said.
"That's what made me think it's definitely something bad."
The family is concerned he may have been in danger due to the company he kept while maintaining his drug habit.
Det Insp Stamper said there was evidence of weapons being used in the fight, but refused to go into any further detail.
There was also some activity in his bungalow after he went missing, and a number of his belongings are unaccounted for including one of his bicycles.
"We've only got a couple of versions of what happened at the moment. Clearly, we need to build a bigger picture," Det Insp Stamper said.
"If someone was there and is aware of an incident that happened and they weren't part of it, we'd like them to come forward."
He said Mr Farrell's mother and two sisters needed closure on what happened to him.
"If that was, as what we think, a violent crime (we will) bring the persons that committed that before the courts," Det Insp Stamper said.