On most mornings, Milena* would have been alone in the car park of the south-western Sydney community centre where she worked with torture and trauma survivors.

But on this Tuesday in August 2015, the 34-year-old's colleague Martha Knox-Haly was running 10 minutes late because she had stopped to get her car washed so that it would be clean to drive a client to an appointment.

"We were unbelievably lucky with the timing," Dr Knox-Haly told The Sydney Morning Herald.

"Milena would be dead if it wasn't for that."

Dr Knox-Haly, a clinical psychologist and former University of Sydney academic who was counselling refugees at the centre, is a woman you want to have around in a crisis – not that she considers herself extraordinary.

"I'm just an ordinary working mum from the inner west," said Dr Knox-Haly, who also happens to be a trained martial arts instructor.

"There's nothing remarkable about me. I'm a workhorse."

Vaughan was, by his own admission, "in an absolute rage" when he set off at 6.50am on August 18 in his black Peugeot and lay in wait for his estranged wife around The Horsley Drive in Carramar near Villawood.

The couple, who had been married for almost three years, had fought over financial issues and separated in June when Vaughan asked Milena to move out of their Wentworth Point apartment.

A sessional lecturer in industrial design at the University of Technology, Sydney, Vaughan was being treated for a major depressive illness and had become obsessed with his wife and fixated on the idea she was seeing someone else.

She had spoken to the police twice in June, saying she felt "unsafe to go outside" and she did "not want [Vaughan] to contact me ... I am worried what he will do because he is very controlling".

On June 18, her sister in Colombia had received an email from an apparently bogus account in which the sender said they hoped Milena died in a car accident.

In July, Vaughan was interviewed by police and denied he was a danger to his wife, and said he did not express that sentiment in the email. He said Milena had mental health issues.

Days later, on August 17, 2015, the 41-year-old sat down at his computer and googled his estranged wife's name, the name of her workplace and "carotid artery neck".

The scene in the car park on August 18 made Dr Knox-Haly stop in her tracks.

She saw Milena's "little red car" – a Daihatsu Charade – pull into her usual spot outside the community centre. The black Peugeot followed immediately behind it.

"I thought, 'This doesn't look right.' It looked like road rage," she said.

She saw Vaughan get out of the car and drop to his knees in front of Milena, who remained seated in the car with the door open and her feet on the ground. "I miss you," he told his wife.

He was "pretending to sob", Dr Knox-Haly recalled, but he turned to her dry-eyed when she asked Milena if she was all right and said: "She's fine. I'm her husband."

Dr Knox-Haly believed Milena was motioning for her to leave, and started to walk away. She discovered later that her colleague was asking her, under her breath, to stay.

Shortly after, she heard "incredible screaming" and turned around to see Milena being "pulled out of the car" and Vaughan lunging at his estranged wife with the knife.

Dr Knox-Haly said she was "terrified" but knew she had to act.

"I thought, bluff, bluff," she said. "I tried shouting at him in the loudest, angriest voice I could muster."

She pulled Vaughan off Milena, who "fell to the ground" with stab wounds to her head, chest and arm. Vaughan then turned around, pushed Dr Knox-Haly and stabbed her in the skull.

"He then ran back towards his car," Dr Knox-Haly said.

Milena had collapsed next to the rear bumper of a parked car when Vaughan accelerated into her, crushing her between the two cars, before reversing and driving into her again.

"I saw him crush her head," Dr Knox-Haly said.

He then sped away from the car park. Milena suffered multiple stab wounds and fractured ribs, a fractured shoulder, several fractured vertebrae and a fractured pelvis.

"It's a small miracle she can walk," Dr Knox-Haly said.

Dr Knox-Haly bears a scar from the stab wound to the head, which required stitches, and said she "cried every day for about 10 days after it happened". She returned to work after three weeks.

"I know what to do to recover from trauma," she said.

On Friday April 27, Vaughan was sentenced in the Parramatta District Court to a maximum of 21 years for grievous bodily harm with intent to murder Milena and wounding with intent to cause grievous bodily harm to Dr Knox-Haly, after pleading guilty in August last year.

He will be eligible for parole in 14 years, on August 18, 2029.

"It will stay with all of us for the rest of our lives," Dr Knox-Haly said.

* The Herald has chosen not to publish Milena's surname.

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