Mother confirmed a suspect in alleged domestic violence stabbings

The death of a five-year-old boy, and the stabbing of two other children in the Blue Mountains is being treated as a domestic violence incident, police have confirmed.

Emergency services were called to the scene at Valley Heights near Springwood about 1pm on Sunday after walkers discovered the group of four in a parked car.

The five-year-old boy died at the scene, while two younger children and a 42-year-old woman were found with stab wounds.

They underwent surgery and remain in hospital in a critical condition.

NSW Police Deputy Commissioner Peter McKenna said all children were siblings, with their mother now a suspect in the domestic violence-related matter.

"I can state that the female is the mother of all three children and is a suspect," he said.

Deputy Commissioner McKenna said the four were found in what appeared to be a "random" location, and investigations into the incident were ongoing.

He said she was not previously known to police.

'Horrific' weekend in NSW

The incident followed three other alleged domestic violence-related deaths in NSW over the weekend.

Police say two women, aged 90 and 23, were fatally stabbed in separate incidents at homes in Bondi Beach in Sydney, and Kooringal in Wagga Wagga.

A third woman, aged 70, was found dead at a property in the state's Northern Tablelands region.

Deputy Commissioner McKenna said the community had been heavily affected by the incidents.

"In my career, I don't think I have seen a weekend like this or a 48-hour period," he said.

"Such tragedy, such horrific events that have touched the whole community."

He said none of the alleged offenders charged over the incidents were previously known to police.

"Because they weren't known to us, means we weren't in a position to be in the preventive space," he said.

"Four different incidents, all completely separate, all with tragic outcomes, just shows that domestic violence doesn't know postcodes, doesn't know what people do for a living.

"If people out there have any concerns about anyone, we would encourage them to speak up and report matters so that we can get into this space and can try and prevent these matters from occurring."

'Unacceptable levels' of violence

Full Stop Australia provides support for people affected by domestic and family violence, with CEO Karen Bevan saying it had been a "really tough morning" for those working in the space.

"I think everyone in NSW is waking up feeling overwhelmed by what can look like an insolvable problem," she said.

"We're thinking as a community, we all have to rise to this and start to think about how we can make a difference."

Federal Minister for Women Katy Gallagher said domestic violence prevention continued to be a priority for government.

"There is no easy solution, if there was one we would have already put it in place," she said.

"More money’s part of it, we’re doing that but again it’s a whole of community response that’s needed to end violence and to stand up and talk about the level of violence in our community right now, which is at unacceptable levels."