THE knife-wielding woman shot dead by police yesterday outside a Hungry Jack’s outlet had Asperger’s syndrome.

Courtney Topic, 22, was said to be acting like a “zombie” before police opened fire, and apparently ignored police calls to drop her weapon.

The Daily Telegraph now reports the young woman had been diagnosed with Asperger’s, a condition related to autism that can mean sufferers have difficulty relating to other and can have trouble understanding instructions.

Ms Topic was shot in the chest after she was seen wandering in and out of traffic brandishing a large knife in the Sydney suburb of West Hoxton about 11.45am yesterday.

Witness Robert Duncan from Penrith said the young woman, dressed in jeans and a T-shirt and casually sipping from a takeaway cup, ignored police calls to drop her weapon, reports.

“The woman then started moving towards them in a zombie like fashion and the police kept their guns on her and kept moving back, she came towards them wielding and swinging a knife,” Mr Duncan said.

“The woman came so close to one of the officers that he was going to be stabbed or had been stabbed and then I heard a pop sound and she went to the ground.

“She could not have been tackled, the way she was running and swinging the knife it would have been ­impossible to get an arm or leg shot on her … she just kept coming as if she was possessed.”

While police said the constable fired only one shot, other witnesses claim two were fired after the woman lunged at officers.

“We heard police talking to her trying to get her to put her weapon down,” witness Alan Sobbi told AAP.

“Then she moved forward and then ‘bang, bang’, two shots were fired. The police went over to help her, to revive her.”

Resident Nicole Maher heard what sounded like two gunshots and rushed down to the scene.

“I know there is bad in the world but in the end, the young girl didn’t even get a chance to make up for her wrong,” she said.

A critical incident team from the State Crime Command’s Homicide Squad and assisted by investigators from South West Metropolitan Region are investigating.

AT 6PM: Exclusive pictures of moments before girl with knife shot dead by police http://t.co/4nED7D18jV #WestHoxton pic.twitter.com/9kQjd8qxMi — 7 News Sydney (@7NewsSydney) February 10, 2015

Critical incident investigation launched after the death of a woman during a confrontation with police. #WestHoxton http://t.co/cAHCdYUvM3 — NSW Police (@nswpolice) February 10, 2015

Assistant Commissioner Frank Mennilli said a constable fired just one shot at the woman.

“One of the police officers resorted to using a firearm, discharging one shot, striking the female to the chest,” he said.

“This is a tragic situation and we are still in the process of contacting the family.”

Officers were called to the intersection of Cowpasture and Hoxton Park Rds, where they say the woman was involved in a confrontation with police.

Police tried to taser the woman and used capsicum spray on her before a male officer opened fire. One report suggests large sunglasses she was wearing deflected the capsicum spray and the taser, fired by a female officer, appeared to have no effect.

A worker at a nearby business told news.com.au paramedics tried frantically to revive her.

“They were doing CPR on her, it was pretty full on.”

A NSW Ambulance spokeswoman confirmed the woman died from a gunshot wound at the scene shortly after.

Witnesses earlier reported that the woman repeatedly lunged at officers who were trying to taser her.

Angela Martin, who was stopped at traffic lights outside the restaurant, told the Daily Telegraph she saw the girl running from police.

“I heard the shot as I was in my bag getting my phone out,” Ms Martin said. “I had no idea what was going. I knew someone had been shot, I saw someone fall and saw all the cops run to that person.”

“Next thing there were cop cars everywhere, it was a nightmare,” she added.

“There were four or five police bent over (her). There were a number of other cops standing by watching.”

She said it was “the worst thing I’ve witnessed in my whole life”.

Police addressed the media at 3.30pm local time where they confirmed a male constable “resorted” to using his firearm after the use of capsicum spray and a taser.

“There were a number of tactical options deployed and one officer resorted to using his firearm,” Assistant Commissioner Frank Mennilli said.

Mr Mennilli refused to go into specific detail about the incident but did confirm that the woman was 22-years-old, lived in the local area and had been walking around with a “large kitchen knife”.

Mr Mennilli said the police presence was necessary. “You’re better going too big than going too small,” he said.

The officer who shot the woman is “distraught” but has yet to be formally interviewed, Mr Mennilli said. He passed on his condolences to the family and friends of the deceased.

All information will be provided to the Coroner who will determine the cause of death and make any findings about the events leading to the woman’s death.

Hungry Jack’s have referred all inquiries to NSW Police.