A rural Auckland family sheltered "in lockdown" in a bathroom when police with guns began to mass outside their home.
The police say they went to the property near Pukekohe about 9am on Sunday to serve a protection order on a man at the house and to seize numerous firearms.
The collection includes military-style weapons and collectible items such as muskets.
The man, who is in his 50s and whom the Herald cannot name for legal reasons, said no protection order was served and he now plans to file a complaint with the Independent Police Conduct Authority.
He believes the police acted unlawfully by entering his property when its gate was locked.
He told the Herald: "I have threatened nobody. I'm a peaceful man."
He lives at the house with his wife and children.
A former police officer, he listed the police resources deployed against him, which he believed were excessive: two trucks of special tactics group officers, five police cars, six uniformed police officers "surrounding the house" who were armed with pistols and wearing vests - "and a guy with a sledgehammer".
He said police were at his house for more than four hours.
Inspector Dave Glossop, the area commander for Counties Manukau south, said the man refused to admit the police.
"Based on all the information available to police - including the presence of a large number of firearms at the address - the Armed Offenders Squad was consulted with and deployed to assist in a support role along with the police negotiation team.
"Under section 18 of the Search and Surveillance Act, police gained peaceful entry to the address.
"More than 30 firearms were uplifted, and the protection order was served."
The act permits entry, search for and seizure of firearms without a warrant for reasons including the existence of a protection order against the person or there being grounds to make an application for one.
A senior police officer negotiated with the man by text message.
In one message, the officer said: "This is getting close to me forcing entry into the house. I don't want to do that. Please come to the door."
The man said his family were terrified by the experience.
"My daughters were crying, my wife was crying."
The mother said her daughter was in tears.
"She was worrying they were going to hurt the dog."
The man said: "We were in lockdown in the bathroom. My mate rang to say, 'It's getting serious, they're putting bullet-proof vests on, there's the Armed Offenders Squad and sledge hammers'.
"I thought, 'I don't need to put my family through this'."
The man, speaking to his friend by phone, asked his friend to pass the phone to a police officer, who then spoke with the man.
The man cooperated with the police and arranged for a neighbour to help the police get his guns.
The man said the police took 39 guns, including military-style rifles, pistols and collectible items such as muskets. They were all secured in two safes.