Clare Nowland, 95, was hit with a Taser at an aged care facility in the early hours of Wednesday, after she allegedly failed to drop the knife.

NSW Police Commissioner Karen Webb on Saturday said Mrs Nowland remained in a stable condition.

"But certainly the next few days will be critical and is likely to be very difficult for the family, and my condolences and thoughts are with the family," Commissioner Webb said.

Commissioner Webb said the "best detectives in NSW" were on the case and she would provide updates on the investigation to the public as she could.

However, it was too early to say whether charges should be laid, she said.

The NSW police declared a critical incident on Wednesday, which means the homicide squad will investigate and the Law Enforcement Conduct Commission will monitor progress.

Commissioner Webb said the officer involved in the incident was not in the workplace, but would not say why.

"We need to ensure that the officers involved in this matter are afforded procedural fairness and anything we say we don't want to prejudice the investigation," she said.

Mrs Nowland was receiving end-of-life care in Cooma District Hospital surrounded by her distraught family after being critically injured during the incident.

Commissioner Webb said she had travelled to Cooma on Friday to be with Mrs Nowland's family.

"It was more important to me that I was with the family yesterday than be in front of the media," she said.

Staff from the Yallambee Lodge nursing home called police after Mrs Nowland, who has dementia, is 43 kilograms and uses a walking frame, allegedly took a serrated steak knife from the kitchen into a small treatment room.

Police and ambulance paramedics allegedly tried to get Mrs Nowland to drop the knife before a senior constable fired his Taser once as she slowly approached them, Assistant Commissioner Peter Cotter said on Friday.

She fell and her head struck the floor.

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"This is a very live and very serious investigation which the Homicide Squad is investigating, and in the rights of everyone involved, the investigation process has to carry on," Mr Cotter said.

The officer who fired the electric shock weapon joined the force 12 years ago and has been taken off active duty.

The critical incident investigation has been elevated to "level one" due to Mrs Nowland suffering an injury that could lead to her death.

Mr Cotter had declined to say whether the officer might face criminal charges, saying it would breach procedural fairness.

The assistant commissioner said he had seen the body camera footage and agreed with a family friend it was confronting. He has declined to release it publicly.

Commissioner Webb on Saturday said she had been informed of what was in the footage and had determined it was not necessary for her to view it.

"Body-worn [video footage] is subject to legislative requirements around the Surveillance Devices Act and other things. So it's not routine and we don't intend to release it unless there's a process at the end of this that would allow it to be released," she said.

with AAP