Friday's terror attack is said to have involved a modified AR-15 style rifle.
Many consider this a military-style assault rifle, but what are assault rifles?
The definition is much debated.
Kiwi gun laws are mostly concerned with how fast a firearm can fire and how many bullets its magazine holds.
They restrict pistols and weapons that fire bullets continuously or are semi-automatic — meaning the trigger must be pulled with each shot — and fitted with magazines holding more than seven bullets.
These are classed as military-style semi-automatics, and people must meet extra requirements to own them.
But semi-automatic weapons with magazines holding seven or fewer rounds and single-shot weapons, which need a new bullet manually loaded into them after each shot, are less tightly controlled. Any one of the about 250,000 Kiwis with a standard firearms licence can own these.
Critics say there are a number of loopholes with such gun laws.
AR-15 style rifles in particular have become notorious as a weapon of choice for mass shootings around the world, being used at Sandy Hook, Las Vegas and San Bernadino.
The main difference between civilian AR-15 rifles and military M16 and M4 rifles is the military models can be fired in automatic or "burst" fire settings. Yet despite its similarities to military assault rifles, anyone with a firearm licence can own an AR-15.
It's made AR-15s popular as fast-shooting, powerful and lightweight weapons with little recoil.
And, while standard licence holders are not permitted to fit their AR-15 with magazines holding more than seven bullets, larger magazines can be imported from abroad without checks.
Another loophole allows high-powered, armour-piercing sniper rifles to be imported by any licence-holder. Nicole McKee of the Council of Licensed Firearms Owners says it will work with the Prime Minister on "well-investigated" gun law reforms.
She understands why hunters using semi-automatic AR-15 rifles say they're needed, especially when hunting deer or other larger animals.
But Miles Anderson of Federated Farmers said there was no place for AR-15s on farms. "They are military-style assault weapons, why would you use them on farms?" Most farms had low-powered single-shot or bolt-action 0.22-calibre rifles for pests, he said. Some had 0.22 semi-automatic rifles.
Chris Cahill, president of the Police Association, wants to ban all high-powered semi-automatic weapons greater than 0.22 calibre.
• New Zealand gun laws are mostly concerned with how fast a weapon fires and how many bullets can go in its magazine.
• Automatic or burst-fire weapons are already restricted.
• Most semi-automatics regardless oftheir power are freely available to 250,000 licence holders, provided they are fitted with magazines containing no more than seven rounds and have no other military modifications.
• Hunters say high powered semi-automatics—which need the trigger to be pulled for each shot— are amust for large game, such as deer, and for sport.
• But critics argue current gun laws allow Kiwis access to military-style assault rifles, such as AR-15s, that are closely related tomilitary M16s and M4s.
• Critics say gunowners should be restricted to owning single shot or bolt action weapons that require each round to be manually loaded into the weaponafter each shot.
Family say there are two people who may have information but are yet to be located.