LATEST: The victim of a deadly shark attack was a local Muriwai man aged in his 40s, police say.
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Inspector Shawn Rutene said the man had been swimming alone from Maori Bay to Muriwai Beach, several hundred metres from shore, about 1.30pm.
A four-metre shark, described as broad, fatally attacked the man.
Rutene said the man's wife and family were distraught. It took police and Muriwai lifeguards about 30 minutes to recover the body as two sharks circled.
In tragic twist, the three lifeguards recovering the body knew the victim.
Rutene said a police officer fired at the two sharks.
"We don't know whether he hit it, but it rolled off and disappeared."
Police were unable to confirm the species of shark, but DOC confirmed great whites had been spotted in the area as recently as the weekend.
Muriwai Surf Lifesaving chairman Tim Jago said the three lifeguards helping police, two aged in their twenties and one in his forties, knew the victim.
Lifeguards were shocked by the size of the shark, he said.
"It's one of the hat. No one seen anything this big out here ever."
Beaches north of Manukau Harbour will be closed for next two days, including Piha and Muriwai beaches.
Helicopters will patrol the area until tomorrow morning and lifeguards will have a strong presence.
Jago said they have used every available 'closed' beach sign to alert beachgoers.
The risk would be reassessed in two days.
The name of the deceased man would not be released until all next of kin are advised.
WITNESS TO ATTACK
A witness has described a police officer firing 20 shots at a shark which attacked and killed a person at Auckland's Muriwai Beach today.
Fisherman Pio Mosie told Stuff that he saw a man swimming nearby.
"All of a sudden... we saw the shark fin and next minute, boom, attack him then blood every where on the water," he said.
He called 111 while his mate ran to get help.
"He was still alive, he put his, head up, we called him to swim over the rock to where we were.
"He raised his hand up, and then while he was rising his hand up we saw another attack pull him in the water.
"He came back up, his head was on the water... then we notice he was already dead."
He heard the police then fire shots from the police helicopter and a few shots from the life guard boat.
"I don't know if they got the shark, killed the shark or not."
Emergency staff confirmed the person's body had been pulled from the water following the early afternoon attack. The shark had been killed but was still floating in the water.
Wellington student, Stef McCallum, 18, said they were first aware something was wrong when a man ran across to the surf club to get help.
A woman told us a man had just been killed by a shark, she said.
"She said there was a big pool of blood in the water."
McCallum said they saw a police officer go out in a surf boat and shoot the shark.
"He fired about 20 shots."
Around 200 people were on the beach and people quickly ran.
"Everybody was evacuated from the water. Word of mouth, 'shark', and everybody left the water."
TV3 reported from the beach that as many as three sharks may have been involved.
A witness told them he spotted the lone swimmer while he was out fishing at the beach, shortly before 2pm.
The distressed man signalled for help when he was attacked by a shark, before he was pulled underwater.
At this point, the witness said three or four other sharks appeared in the area.
Other surfers reported a large shark in the water at the rivermouth at north Piha today.
"We thought it was pretty cheeky because it was right in the surf line, heading north," one said.
A staff member at Sand Dunz dairy said people were coming into the dairy "speechless".
"I'm shaking, I don't really want to talk about it," the shop assistant, who didn't want to be named, said. "Everyone's speechless."
Earlier this week surfer Bourne Nobel Buiski posted on Facebook that there had been a "massive" shark spotted near surfers on Monday at Piha, 14 kilometres south of Muriwai.
He said that a local man ran out of the water "white faced and terrified".
"He was saying that a great white, a massive great white had just swum right beside him," Buiski said.
No one believed him, he said.
"As they are so rare here. There were about 60 people there, and no one came in."
A local resident, who did not want to be named, said Muriwai had always had sharks.
''Out the back of Oaia Island is a huge crater on the ocean floor and fishermen say they have seen huge sharks in the area and will not go diving there.''
The beach was crowded with children from Glen Eden Intermediate and Avondale College, a Fairfax reporter on the scene said.
Auckland City Council said the beach had been closed for the day.
Piha Beach, south of Muriwai, had also been closed, lifeguards said.
A Surf Life Saving spokeswoman said lifeguards had not spotted sharks at Piha in the past week.
She referred all questions relating to the shark attack to police.
NZ SHARK ATTACKS
There have been 14 known fatal shark attacks in NZ, since records began around 1837, according to Department of Conservation shark expert, Clinton Duffy.
"In the last 20 years we have been averaging two shark incidents, where the shark actually bites someone, a year."
"Those are generally on swimmers and generally result in fairly superficial flesh wounds," Duffy said.
The last death was in 2009, when a kayaker was mauled by a great white in the Coromandel - whether he drowned before the shark found him is still disputed. Before that the last death was in 1976.
Global shark attacks have increased every decade since 1900. Last year's 12 fatalities, three in Australia, was almost three times the average of 4.3 from 2001 to 2010, according to the International Shark Attack File.
There are more than 60 shark species that come to New Zealand waters. The majority are little-known species that live deep below the ocean surface.
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