Anyone who's bought an assault rifle in the past week should be expecting a knock on the door from the police soon.
So should gun clubs, says Police Minister Stuart Nash.
"If you've bought one of these AR15s, AK47 or assault rifles with your stock-standard firearms license and you don't hand it in, expect to get a knock on the door from the police," he told Newshub Nation on Saturday.
The Government took just six days to announce the first round of gun law changes after the Christchurch terror attack, in which a man armed with semi-automatic weapons murdered 50 people and injured just as many.
The massacre has seen an outpouring of grief and defiance across not just New Zealand but the world.
Nash told Newshub Nation the authorities know who already owned E-category rifles - military-style semi-automatics - before last Friday's atrocity. A number of guns previously categorised 'A' have now been moved into 'E', but there are no records of who may have bought them in the six days since the massacre.
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There were reports of panic-buying ahead of the law changes, which were widely expected.
"What the police can do, under the law, is go to dealers and ask for five years' worth of records - because dealers have to keep a record of everyone they've sold a gun to - and then go and knock on the door," said Nash.
In a few weeks, when the legislation is passed, all military-style semi-automatics will be banned. Owners who've previously bought them legally will be compensated when they hand them over. Dealers won't.
"We expect that they will sell them back to their suppliers overseas," said Nash.
A former soldier last week said he attended the same gun club as the suspect, and described members' attitudes towards firearms "pretty scary - especially with the E category ones".
"It was like being at a 1980s NRA meeting. It was the perfect breeding place for this kind of thing," Pete Breidahl told Newshub.
Nash said gun clubs would also be under the microscope, as the Government investigates what else it can do to prevent another tragedy.
"Do we need to be a little stricter there?... We're looking at all of this sort of stuff and seeing if it's robust enough, if we need to do more or if the regime we've got in place is sufficient… Cabinet hasn't considered anything on this point at this point in time. I'm sure that we will hear more going forward."
The suspect is expected back in court in April. Deputy Prime Minister Winston Peters has promised if he's found guilty, he'll spend the rest of his life in isolation.