A New Zealand-born nurse ambushed and killed on the veranda of her home in an upmarket Sydney suburb was possibly the victim of a man who preyed on her.

Michelle Beets, a nurse for almost 40 years, had dedicated her life to helping others, but no amount of expertise could protect her when she was confronted by a killer on her doorstep.

The injuries Ms Beets suffered on Tuesday night were so brutal that the two people who discovered her were helpless to save her.

Police would not say how the 57-year-old was murdered because it was too graphic and distressing for her family and friends to bear.

Yesterday, they confirmed they were aware Ms Beets and other nurses at Royal North Shore Hospital, where she was the emergency department nursing manager, might have been having trouble with a mentally ill outpatient.

Ms Beets' older brother, Marty Beets, who lives in Papatoetoe, said an alarm went off at his sister's house and their security service called her partner, David Grant, to ask if staff should go there.

He told them not to, because he would be home in a few minutes.

Mr Beets told the Herald of the "chilling" moment when he learned Michelle had been murdered.

"The phone went off at about 4 o'clock in the morning - a call at 4am, you know it's not good. I got to the phone but missed it and my sister [Robyn] was already on the answering machine saying she had bad news. It was chilling."

Mr Beets said Michelle had been dedicated to her work as a nurse but could also be "a bit of a hard case".

"She used to work at Middlemore Hospital and she went right to the top, to theatre nurse. She was always making sure things were done correctly.

"She was very precise and orderly, but if you got her at the right time, she'd have a few jokes up her sleeve. She was a hard-case girl."

Mr Beets said he was "totally angry" at the attacker and urged him to "man up" and hand himself in.

Mr Beets is to fly to Australia - where his father and two younger sisters also live - for the funeral.

Michelle Beets attended Epsom Girls Grammar School in Auckland and also worked at Green Lane Hospital before moving to Britain.

Her father, Robby Beets, 87, told the Sydney Morning Herald his daughter was "very dynamic", could not stand fools and was always rushing about.

"She was never fashion-conscious. She just ate, slept and dreamt nursing. She took me to the hospital to visit old people to let me know how lucky I was to be still healthy at my age.

"She was really well liked."

Mr Beets spoke to Michelle by phone three times a week and said she was "sometimes too kind".

"She was always on the ball and always helpful. She was too soft, too sentimental and too emotional - too kind. [She] never actually realised there were bad people in the world."

Ms Beets was found dead at home in the leafy suburb of Chatswood after neighbours heard screaming about 6.20pm on Tuesday.

A couple walking their dog in the affluent, low-crime northern suburb saw a man dressed in a green hooded jacket and carrying a backpack running away from the scene shortly before her body was found.

Ms Beets had just been asked by the New South Wales Nursing Association to join an expert panel it was convening to research emergency nursing.

"She was bright and breezy but was busy and said, 'I'm happy to help you. I'll be at my desk first thing in the morning. Call me then'," said association assistant secretary Judith Kiejda.

For the past 25 years, Ms Beets had worked at Royal North Shore. A spokeswoman said staff had lost a valued and esteemed colleague, friend and mentor.

"Ms Beets was an exemplary nurse, a dear friend and teammate," she said. "We are devastated by her loss."

Ms Kiejda said colleagues had described Ms Beets as a "nurse's nurse" who had been a passionate advocate for her staff.

"It [the murder] is so senseless - a senseless waste of life when we can't afford to lose these sorts of people."

- ADDITIONAL REPORTING: AGENCIES