Trigger warning: This article contains descriptions of domestic violence

A mother remains in critical condition after what police suspect was an attempted murder suicide involving her three children.

A cyclist was the first person to come across what NSW Police Deputy Commissioner Peter McKenna described as a “barbaric” scene inside a car parked on the side of Waratah Rd at Valley Heights in the Blue Mountains about 1pm on Sunday.

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The passer-by attempted to save the lives of children, who had all been stabbed inside the car — but only two of the three children, all aged under five, survived.

They remain in a critical condition after suffering life-threatening neck wounds.

The mother in her 40s was also found fighting for life.

“We will allege her condition is the result of self-inflicted wounds, so we have to wait for the medical side of things to play out,” McKenna said on Monday.

If she survives the injury, he said: “Detectives will look to speak with her with the intent of charging her with homicide.”

‘Can’t remember a weekend like this in my career’

The suspected murder suicide was one of four horrific incidents to take place across the state over the weekend.

“I can’t remember a weekend like this in my career,” McKenna said.

“It is really overwhelming.”

Police allege domestic and family violence was behind three deaths on Saturday — 90-year-old grandmother, Valentina Spivak was stabbed 19 times in Bondi Beach unit, a 23-year-old woman was stabbed in Wagga Wagga, and a 70-year-old woman was found dead in a fire-damaged home in Mole River.

If you need help in a crisis, call Lifeline on 131114. For further information about depression contact beyondblue on 1300224636 or talk to your GP, local health professional or someone you trust.

If you or someone you know is impacted by sexual assault, domestic or family violence, call 1800 737 732 or visit 1800RESPECT.org.au. In an emergency, call triple-0.