Five members of a well-loved family were slain in a targeted and "extremely personal" attack in Sydney's leafy northwest, police say.
Chinese-born Min Lin, 45, his wife Yun Li Lin, 43, two sons, Henry, aged 12, and Terry, nine, and another female relative aged 39, were bludgeoned to death at their secluded property in North Epping some time between midnight and 9.50am (AEST) on Saturday.
Daughter Brenda Lin, 15, returned to Australia after a trip from China on Sunday morning.
NSW Homicide Commander Geoff Beresford said it was unlikely the attack was random.
"[The house] is somewhat hidden from the street, being a battle-axe [shaped] block, but I'm more concerned with the injuries to the people themselves that leads us to think that it is targeted," Detective Superintendent Beresford told Sky News.
He said the Lins could have known their attackers.
"It appears to be an extremely personal type of attack, given the level of violence but ... we're open-minded, we can't make any particular prediction this early in the inquiry," he told Sky News.
Police forensic teams sweeping the Lins' Epping home, as well as post-mortem examinations on the bodies, may help piece together how and why the horrific attacks took place.
"It certainly appears that all the injuries were blunt force trauma to the upper bodies and to the heads of the victims," Superintendent Beresford told reporters this morning.
He described the murders as "a terrible tragedy" and added that police had not established any link between the family's murders and Mr Lin giving evidence of an armed robbery on a Chubb armoured van at the Epping Club opposite the newsagency earlier this year.
"It is extraordinary, it's extremely violent and certainly unusual in my experience to have this many people murdered on one occasion," Superintendent Beresford said.
He said police had no persons of interest.
Police were speaking to members of the Chinese community and relatives of the victims, including the parents' daughter.
Tributes have poured in for the hardworking Lin family who ran the Epping Central Newsagency in Rawson St, Epping, for more than six years after migrating from China.
Former NSW Epping MP Andrew Tink, who had an account at the newsagency, described the Lins as a "quiet, hardworking and self-sufficient" Chinese migrant family who ran the business for more than six years.
"I knew them very well, very well," Mr Tink told AAP.
While serving as the local MP, Mr Tink would stroll across the road from his electorate office each morning to buy newspapers.
"He [Mr Lin] didn't impose himself, he was always happy to have a chat," Mr Tink said.
"He never had an axe to grind or anything like that, he was just a very pleasant guy who was very happy to chat."
He confirmed the names of the dead parents.
"There's still a huge question mark about what exactly happened," he said.
Local residents and business people placed dozens of cards and bunches of flowers outside the newsagency over the weekend.
"Thank you for your good and generous help in our Epping Community," one card read.
"Your generosity will not be forgotten. Please know that you have touched many people's lives," said another.