The estranged family of the man found dead under rubbish at a house on Sydney's lower North Shore have described him as a "good man", but someone who often fell on the "wrong side of the law".

Homicide detectives spent Wednesday speaking with the family of Shane Snellman, whose remains were rolled up in a carpet and found at a deceased estate in Greenwich last Tuesday, as they try to piece together his last movements.

Police believe the badly decomposed body had been there for many years before the property owner Bruce Roberts died from natural causes last July.

However, the exact time period is yet to be determined.

Mr Snellman's estranged nephew Anthony Trudgitt, who spoke to the ABC on Wednesday, said he last saw his uncle at a family gathering at Arncliffe, in Sydney's south, six years ago.

"We were at my Nan's house, who's my great aunt, and Shane was there," he said.

"But he didn't say much — he was in and out of jail for criminal stuff, so he kept to himself."

He said Mr Snellman's half-sister Tracy Trudgitt found out about her brother's death when detectives turned up at her Macquarie Fields house on Friday night.

"We saw the Greenwich murder on the news earlier in the week, and we both commented something like, 'that's someone's brother or friend', it was just horrible and really creepy," he said.

"On Friday night, at around 10:00pm, there was a knock on the door and one of the detectives told us it was Shane's body. Mum immediately collapsed and burst into tears — family is family, it really hurts.

Police working at the house where Mr Snellman was found ( AAP: Danny Casey )

"He had a really hard life — he was in foster care and then he ended up in prison — he was always in trouble for something," Mr Trudgitt added.

Guns and a mobile phone were seized from the Greenwich home, and police believe the evidence could be crucial in solving a murder that has left them baffled.

Neighbour Gayle Meagher said detectives asked her whether she heard gunshots fired in the area over the last decade.

"It's hard to tell because often you think these loud sounds are from a car backfiring," she said.

With a history of petty crime, police are now investigating whether Mr Snellman was shot and killed during a break and enter at the Greendale Street address.

Neighbour Edna Scott said she noticed Bruce Roberts had became increasingly paranoid about security up until his death last July.

"He was always putting up extra barbed wire," she said. "I thought it was to help maintain his garden, but he was such a recluse and a hoarder, that I often wondered what was going on."

Bruce Roberts remains a suspect in the ongoing murder investigation, after severe injuries were found on Mr Snellman's badly decomposed body.

A body was discovered in a Greenwich home on May 29, 2018, less than one year after the former occupant died. Police believe the body may have been hoarded by the previous occupant Bruce Roberts. ( ABC News: Mark Reddie )

The ABC understands that Mr Roberts left part of his will to a cousin, who lives on a property in far central western New South Wales, and the majority was donated to a number of charities.

Forensic cleaners have resumed the mammoth task of clearing out piles of rubbish from the house, which is no longer a crime scene.