A father was woken to his children's screams after their mother allegedly attacked the trio as they slept in their suburban Sydney home.
The 47-year-old woman is under police guard in hospital on suspicion she was trying to kill the three children - aged 10, 13 and 16 - during the attack on Monday morning.
She allegedly turned the knife on herself following the stabbing.
"Until we have an opportunity to speak to her we won't know what her intent was," Detective Superintendent Naomi Moore told reporters.
"But we're certainly taking it as a potential attempted murder."
The father and the children - one of whom has paraplegia - were all in their bedrooms of the family home at Baulkham Hills, in Sydney's northwest, during the attack, police said.
The incident which woke the father was "completely unexpected", Det Supt Moore said.
"Upon waking up to what I would believe to be a number of screams or yells, he has ... secured the weapon and he's contacted police," she said.
"There's certainly no domestic violence history reported to police ... there's no AVOs (restraining orders).
"This is the first time police have responded to the house for any type of domestic situation."
The woman was believed to have been behaving "a little bit erratic" in the days before the stabbings, Det Supt Moore said.
A 10-year-old boy, and two girls aged 13 and 16, one of whom is believed to be paraplegic, were treated by paramedics before being taken to hospital along with their mother.
Footage of the scene showed one of the children being stretchered away with a pink teddy on their lap.
Det Supt Moore said the incident was tragic.
"As sad as it is, we haven't dealt with this family before, and I only wish that maybe we had of, maybe we could have reached out and helped this family sooner," she said.
A crime scene has been established as police investigate the incident.
