The New Zealand authorities have not said exactly what type of firearm was used in the mosque's attacks, but Prime Minister Jacinda Ardern said at a press conference this afternoon that the weapons were "seemingly modified".
The weapons they purchased were two semi-automatic rifles that were part of the arsenal of five guns allegedly owned by the Australian terrorist suspect Brenton Tarrant.
Tarrant had a Category A firearms license, which is the New Zealand weapon license. It's fairly easy to obtain as long as you pass the police background exam and complete a safety course for firearms. The registration of category A firearms is not required. This means that gun owners are able to store as many weapons as they want without being monitored.
The Category A license entitles the holder to purchase more than 2,000 types of firearms, including semi-automatic weapons. You do not have the right to own a military-style semi-automatic military rifle (MSSA) that is restricted to a "Category E" and, if legally owned, must be registered and securely stored.
Ardern's comments, along with earlier comments from Police Commissioner Mike Bush, indicate that Tarrant may have been able to use a high-powered magazine to transform a weapon he was legitimately allowed to possess – a standard semi-automatic rifle – into an MSSA.
Bush told reporters Saturday that a "Class A gun" can buy firearms without the magazines or things that allow them to be in the condition they were. "
Sales of high capacity journals are not regulated in New Zealand.
According to Philip Alpers, an expert on weapons policy at the Sydney School of Public Health, University of Sydney, using a high-capacity magazine would "make these firearms technically illegal … but they would be very easy to acquire."
Chris Cahill, president of the Police Group, welcomed the Prime Minister's early commitment to change the gun laws in New Zealand. "We can not ignore the role of the guns in this event," he said.
Mr Cahill added: "Jacinda Ardern has said emphatically that the New Zealand Arms Law will change, and now is the time for that change. I absolutely agree with her and believe that many New Zealanders will be appalled that someone in our country can pile up a gun shaft as it was discovered in this Christchurch tragedy. "