Lance Burdett. Photo: SUPPLIED
The officer who shot and killed a woman brandishing a hunting knife will have had a split second to react in a "frightening" scenario, a former top police negotiator says.
On Wednesday night, the Christchurch officer first shot and critically injured a man who was carrying a hunting knife and chasing his partner from their Bryndwr home.
They then shot and killed the woman when she picked up the knife and threatened officers.
Police figures showed 55 people had been shot dead by an officer between 1916 and the end of the last year - and just one of those who died was a woman.
Lance Burdett, who led negotiations with Jan Molenaar during the 2009 Napier siege, said officers were trained to use the most effective, least lethal method when they're threatened by someone with a weapon.
"So, you start off with, can a baton be used? Can a taser be used? And then if that's not available, a firearm," he said.
"But when you're in the heat of the moment like that, and particularly if they're in close proximity... you don't have time to get your weapon out, the necessary one that's available."
Officers had to make split second decisions to keep themselves and others safe, said Burdett.
They are trained to shoot at the "centre mass" because it's the largest part of the body - but unfortunately, that is where vital organs are, he said.
"I hear people saying 'why couldn't you shoot them in the leg?'. Well, you try, when somebody's running at you.
"This is not the movies, this is real life and it's frightening."
A hunting knife is a large, dangerous weapon that can do serious harm, Burdett said.
He said a taser or pepper spray might work against a person with a knife but they required distance and time, which an officer didn't necessarily have in such a volatile and rapidly evolving situation.
"When people are highly emotional or on drugs or perhaps in some way mentally disaffected, these things don't work. Neither does communication... because they're not [using] the logic part of their brain they don't receive information the way it would normally be.
"People will be shouting and running around and there'll be a lot happening and you're expected to make a split second decision when things are really, really dynamic."
Police on Clyde Road the day after they fatally shot a woman, and critically wounded a man in Christchurch. Photo: RNZ / Nathan Mckinnon
Police and independent watchdog investigate
Police and the Independent Police Conduct Authority are both investigating.
The officer's decision to shoot would form a "large part" of the investigation, said Canterbury District Commander Superintendent Tony Hill.
Burdett said within a few days, that officer would be formally interviewed "like any other person" as part of a criminal investigation.
"You're given the Bill of Rights, you have the right to have a lawyer with you, and they will go through and interview exactly the same as any other person that's in that situation," he said.
The officer would also be supported by police and the union, Burdett said.
The Police Association President Chris Cahill declined to comment.
Police at the site of a double shooting that resulted in one dead and one critically injured in Christchurch. Photo: RNZ/Sam Sherwood
How events unfolded
Police were called to the Clyde Rd property in Bryndwr, Christchurch about 11pm on Wednesday after a person known to the couple called police to say the man was armed with a knife and threatening to hurt himself and his partner.
When officers arrived, the woman ran out of the house, followed by the man with a hunting knife.
"Police believed the woman was in risk of imminent serious harm, and fired a single shot, which hit the man," Commander Superintendent Hill said.
An officer approached the man to provide first aid, he said.
"The woman has picked up the knife and began to threaten officers, despite an appeal for her to put down the weapon, she has advanced on police, brandishing the knife.
"A second shot was fired, hitting the woman."
Officers immediately provided medical assistance, but she died at the scene, Hill said.
A nearby resident told RNZ the couple were "always fighting", while their church pastor said the community had been devastated by the incident.
The injured man was in a stable condition in Christchurch Hospital.
The police cordons at the scene were lifted on Thursday night.
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