Boolaroo stabbing: New details after a teenage girl allegedly murdered her younger sister in Lake Macquarie region

A teenager accused of murdering her little sister allegedly attacked her younger sibling 'completely out of the blue', police say. 

The 17-year-old was arrested after her sister, 10, was found with stab wounds at Boolaroo, in NSW's Lake Macquarie region, at 3.45pm on Monday.

The 10-year-old girl was treated by paramedics before she died at the scene.

Her older sister was then escorted by officers to Belmont Police Station and the murder charge was heard at Broadmeadow Children's Court on Tuesday morning.

She was charged with murder (DV) and made no application for bail. Neither she nor her family were present in court for the case. 

Homicide Squad Commander Detective Superintendent Danny Doherty said police will allege the attack was random.

'There's no indications from what information we have at the moment to indicate why this [allegedly] occurred,' he told reporters on Tuesday. 

'It's very hard to imagine. It's unthinkable that this could happen to a 10 year old. 

'This is one of those incidents, as far as we know, which has happened completely out of the blue.'

Police said the 10-year-old was allegedly stabbed with a 'sharp instrument' multiple times to her upper body area.

The girls were the only two children in the household and the family had no previous dealings with police for domestic violence matters.

Detective Doherty said the family are still struggling to come to terms with the tragedy and offered his condolences.

'It's tragic circumstances,' he said. 'There's a family who's still grieving, trying to come to terms with what happened. 

'My thoughts go out to a mother having lost her 10-year-old and now has another daughter facing court allegedly responsible.'

The 10-year-old girl's death has rocked the close-knit neighbourhood. 

Neighbours on the quiet suburban street were horrified by the murder charge on Tuesday morning.

Residents largely comprised retirees and young families, while others were people with special needs living in facilities on the street.

The home was on a new development of detached bungalow properties that are largely owner-occupied and nestled in hills.

The quiet estate is normally the scene of people walking their dogs and kids playing, but on Tuesday it was still sealed off by police as forensic experts swarmed over the scene.

One neighbour said she thought the home where the alleged murder took place was a rental because the garden was the only one that wasn’t maintained.

‘My daughter is the same age and she’s freaking out that someone will stab her too, so she’s really shaken,’ another neighbour said.

‘You just don’t think something like this will happen on your street.’

She described the street as quiet and said no one knew much about the family.

One woman trembled as she told Daily Mail Australia she didn’t think there were any children living at the property.

‘There was an older woman and a younger one, maybe age 30 or something, living there but I didn’t see any children there.’

‘The younger one drove one of the cars and she would say “hi” outside but that’s it.’

Ms Forsten said another neighbour had seen the girls at the property during the Christmas period, but they hadn’t been seen at the property since.

‘I’m shaking,’ she said. ‘It’s horrible.’

Another neighbour said: ‘The woman has lost everything.

'She’s lost her family, it’s a tragedy.’

Others who were home at the time of the alleged incident said they didn’t hear any noise coming from the home at all.

‘We thought there were a lot of sirens nearby but they turned them off when coming into the street because there’s no traffic.

'But then they knocked on our door and that’s when we found out it was on our street.’

The crime scene was still in place on Tuesday morning, as police continued investigations.

Photos from the scene show shocked locals gathering outside the crime scene.

A number of police vehicles remained parked in the street as detectives were seen coming and going from the home on Monday evening.

The latest incident follows a spate of unrelated stabbings across NSW in recent weeks.

It's been two weeks since five women and a shopping centre security guards lost their lives during a stabbing rampage at Westfield Bondi Junction on April 13.

Two days later, Assyrian ­orthodox bishop Mar Mari Emmanuel was stabbed at a church in Wakeley in western Sydney, on April 15.

A man, 28, was stabbed in Quakers Hill last Friday night before dying on the way to hospital.