The bodies of a 46-year-old woman and two children aged 12 and four were found in a Campbelltown house.
A father charged with killing his partner and their two children who he cared for full-time had allegedly been planning the murders for months.
Emergency services were called to what police allege was a "particularly violent scene" at a home in Campbelltown, in Sydney's south-west, just before 8pm yesterday, where they found the bodies of a 46-year-old woman and two children, aged 12 and four, inside the home.
9News understands he was the father and full-time carer for the two boys, who both had severe learning disabilities and were non-verbal.
READ MORE: Recall for dessert product that put toddler into coma
The family moved to Sydney from Bangladesh about 10 years ago, and the mother worked full-time.
The accused killer was not known to police and didn't have a history of domestic violence, however police documents allege he had been plotting the murders for months.
That plan allegedly began following the news of a horror double murder-suicide in Perth earlier this year, when two teenage boys, who both lived with severe autism, were killed by their parents.
Acting Superintendent Michael Moroney told Today this morning that police understood "the deceased and the two children were related" to the 47-year-old man charged over their deaths.
"Whilst I can't give you specific information in regards to how they passed, what I can tell you is all three persons sustained significant injuries, and it was a particularly violent crime scene," he said.
Moroney told Today that the house was "described as a very traumatic scene, a very horrific scene".
Officers have removed a number of items have been taken from the home, including a knife that police will allege was the murder weapon.
A 47-year-old man was arrested at the scene and taken to Campbelltown police station.
This morning, police said the man had been charged with three counts of domestic violence murder.
He was refused bail and appeared in court today. He will return to court in mid-July.
Community rocked
Moroney wouldn't go into details about any weapons being seized, saying only "a number of items" were found inside, but no guns.
He said the bodies "were located in various parts of the premises" and it was believed the 47-year-old man called emergency services.
"I haven't listened to the Triple Zero call," he said.
READ MORE: Man fighting for life after stabbing in Sydney
"Broadly, quite broadly, the information was, an incident happened at that location and he was requesting police to that scene."
Moroney said the man had no history with police and there were no offenders believed to be outstanding.
There was no indication of mental health issues, but that would form part of the police investigation.
A large police presence remained into the night on the street, where police had established a crime scene.
The home was cordoned off with police tape, and multiple police vehicles with flashing lights were parked up and down the street.
Police could be seen in the front yard of the home.
Neighbours spoke this morning of their shock and horror at the news.
"My heart sunk and being a mum - not even that, just, two young kids, you know what I mean," one woman told 9News.
Campbelltown detectives are investigating with the help State Crime Command's homicide squad.
Police called on anyone with information to come forward.
The gruesome discovery came hours after police announced hundreds of people had been arrested in a statewide operation targeting repeat domestic violence offenders.
"This today appears to be not something that we had on our radar in terms of being known to police, but I can reassure the public that domestic violence is a number one priority for the NSW Police, and we will continue to prioritise DV offenders," Moroney said.
Support is available from the National Sexual Assault, Domestic and Family Violence Counselling Service at 1800RESPECT (1800 737 732).
UK police investigate child sexual abuse allegations linked to Epstein files
Phone boast got Australia's youngest murderer re-arrested
Is rentvesting dead? Tax reform to push people away from popular strategy
Nine.com.au readers divided over new addition to GP visits
Treasurer reveals why oil crisis hitting one state harder than others
One man dead after five turn up at Sydney hospitals after shooting
$1.6 million bail for son of billionaire he's accused of murdering
Trump finally gives deadline for Iranian strike
Dodgy booze that killed teens found in local liquor stores
Police hunt for youth behind random attack on lollypop man
Opposition leader opens door to potential One Nation partnership
Putin makes mad dash to China as world woos superpower
School students rescued from camp as deluge floods two states
Two Americans arrested after costumed man entered enclosure of viral Japanese monkey
Business owners hail '47 per cent partner' PM in meme trend
Woman dies after being hit by ute in horror Queensland crash
Why massive crowds gathered outside watch stores globally
