Could New Zealand have stopped its worst mass shooting before it ever started?

That's the subject of a new high-level investigation announced by Prime Minister Jacinda Ardern on Monday (March 25).

The Royal Commission of Inquiry will look into events leading up to the March 15 shooting when a gunman killed 50 people in two Christchurch mosques.

(SOUNDBITE) (English) NEW ZEALAND PRIME MINISTER JACINDA ARDERN, SAYING: "While New Zealanders and Muslim communities around the world are both grieving and showing compassion for one another, they are also quite rightly asking questions on how this terror attack was able to happen here.

This includes questions around the accessibility of semi automatic weapons, the role social media has played generally and the focus of the intelligence and security services." A royal commission is an independent inquiry usually used only for matters of the greatest importance to the public.

One analyst told Reuters it would likely cover agencies from customs to police and immigration.

The prime minister wouldn't say how long the inquiry might take.

Ardern has won praise for her leadership following the shooting.

She moved quickly to denounce the incident as terrorism and toughen the country's gun laws.

Meanwhile, visitors were still flocking to makeshift memorials near the Al Noor and Linwood mosques.

(SOUNDBITE) (English) NEW ZEALANDERS FROM CHRISTCHURCH, LIANNE AND IAN HUNTER, SAYING: LIANNE: "The tears don't go away, because so many people are so sad, the children.

Things like this, they don't happen here.

They don't." IAN: "Well, they didn't." LIANNE: "No, we've woken up, yeah, we didn't want to wake up in New Zealand.

It's been a safe place for so long." A suspected white supremacist has been charged with one count of murder over the Christchurch shootings.

He is next set to appear in court on April 5.

Ardern has previously said the man wasn't on any watch lists in New Zealand or Australia.

The prime minister has announced a national remembrance service on March 29 to honour the victims. ENDS