A split-second decision to use a Taser on an armed man, who later died, may have saved the life of two NSW police officers, the state's top cop says.
Police were called to a house in Helen Street, Sefton, just after midnight (AEDT) on Tuesday, following a complaint that a woman had been sexually assaulted.
The call was made from a neighbouring house.
When they arrived, police say they were confronted by a man who was holding two knives - one 23cm in length and the other 29cm - and whom they believed was affected by alcohol.
"In a split second the officers made a decision, which I believe, may have saved their lives," NSW Police Commissioner Andrew Scipione told reporters on Tuesday.
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"One officer, armed with a Taser, was able to discharge the weapon at a close range to disable the offender."
The man was hit in the chest area and fell to the ground before he was handcuffed, he said.
"Had (the officer) not been successful, I certainly believe the consequences could have been tragic for one or both of the officers involved," Mr Scipione added.
The man lost consciousness after he was handcuffed.
Officers performed CPR on him until paramedics arrived, but he died in hospital.
The official cause of death is yet to be determined by the coroner.
Mr Scipione says no deaths to date have been caused by the use of a Taser in NSW.
He did not believe police acted inappropriately during the incident.
"They used the device consistent with worldwide instruction," he said.
"We avoid the head and the groin and all those other areas, so there is no suggestion they have done anything but what was required."
A critical incident team is investigating the incident.
Man dies in hospital
Officers performed CPR on him until paramedics arrived, but he died after he was taken to Liverpool Hospital.
Chief Inspector Glen Fitzgerald of Bankstown Police would bit say how many times, or where on the body, the man had been tasered.
"The circumstances surrounding the Taser, and the entire incident, will form part of the reference for the critical incident team," Chief Inspector Fitzgerald said.
Asked if officers had acted appropriately, he replied: "At this stage ... we are looking after the police in terms of their welfare.
"At this point the police are very comfortable with the circumstances surrounding what has occurred."
Second death in police custody
The man is the second to have died in two days during a police arrest in Sydney.
In the early hours of Monday, St George-Illawarra rugby league fan Steven Bosevski died after he was sprayed with capsicum and hit with a baton by police breaking up a fight at St George Leagues Club in Carlton.
A critical investigation team is looking into the incident.
Three other deaths have been linked to police use of Taser guns in Australia.
Antonio Galeano, 39, died after being stunned with a 50,000-volt Taser during a violent confrontation with police at a unit in Brandon, near Townsville, on June 12, 2009.
Two months earlier a man died in Alice Springs after police used a Taser on him and in May 2002, NSW man Gary Pearce died of a heart attack about two weeks after being jolted with a stun gun while threatening police with a frying pan.
