She said the man was known in the street for having a revolving door of visitors, who would arrive at all hours of the day.
Other residents of the street, which is dotted with public housing homes, said the man had moved into the unit less than a year ago.
Police are probing whether the group had died of a drug overdose, as family members publicly expressed their grief over their deaths.
Late Tuesday morning, a group of police dressed in bright yellow hazmat suits entered the property wearing breathing apparatus and with oxygen tanks strapped to their backs.
Homicide Squad Detective Inspector Dean Thomas said the deceased group were found in the lounge room. One person was a resident, and the other three were visiting, police believe.
Emergency services were called to the property just before 2am. The cause of the deaths is yet to be determined but is not believed to be suspicious.
Thomas said there were no visible acts of violence, but noted there were some injuries on the deceased, the nature of which he declined to detail.
“We don’t know what has caused their death,” Thomas said. “We’ve got to keep an open mind to this. It’s unusual that we find four people deceased in the one property, potentially from a drug overdose, but we’ve got to keep an open mind until we can confirm that’s the case, it could be anything.
“The families will want answers as to what has occurred.”
Thomas described the scene as “very confronting and very traumatic” for the man who found the four people dead and said the process of determining the exact cause of death could take days or weeks.
Police have not yet formally identified the four but believe the men to be aged 37 and 32, the boy 17, and the woman 42. Three of those who died were known to police.
Neighbours last saw them alive on Monday morning about 2am.
Police said items found at the scene would be analysed, and post-mortem examinations will be conducted before a report is prepared for the coroner.
Thomas said he was “mindful” of the synthetic drug fentanyl being linked to overdoses overseas.
Cory, who lives next door to the unit where the four people died, and is the uncle of the teenager, told reporters at the scene he believed the deaths were drug-related.
“It may have been a drug overdose, I’m not too sure,” he told Nine’s Today program. “I found them and it’s tortured me, it’s really got to me.”
“I hope people take a lesson from it not to fall into this type of stuff.”
The man said he knocked on the door of the property in the early hours but could not rouse anyone, so he went to the window and saw his 17-year-old nephew lying on the ground. He then smashed his way into the home where he found the other bodies and called the police.
The boy is the father of an 18-month-old girl, he said.
As he left the scene about midday on Tuesday after speaking to police for several hours, Cory said his family were still grieving the loss of both of his parents, who died within months of each other, in the past year.
“Now I’ve lost my nephew too. It is just shattering,” he said. “Our family have had such a rough time. We can’t catch a break.”
He described his nephew as a “brilliant boy” who had his whole life ahead of him.
“He was just a kid,” he said.
The family embraced outside the grey weatherboard house cordoned off with police tape as the teenager’s distraught mother broke down in tears.
Shortly afterwards, grief-stricken family members were escorted inside by police.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000. The investigation is ongoing.
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