Christchurch attack: Lone gunman theory 'incongruous' - expert

The alleged Christchurch gunman probably didn't act alone, a high-profile security expert has claimed.

Only one person - a 28-year-old Australian white supremacist - has been charged in relation to the March 15 attack, which left 51 people dead.

As soon as the very next day police were saying the killer acted alone, but Paul Buchanan - who has decades of experience researching and teaching on international security issues - has his doubts.

"I happen to think that contrary to the official narrative that he acted alone, there may have been others involved one way or another," he told The AM Show on Monday.

Newshub on Sunday night aired the first of a series of reports looking into New Zealand's white supremacist community. National correspondent Patrick Gower said he'd been looking at about 200 individuals with links to extreme pro-white views, describing them as "just a fraction" of what's out there.

Dr Buchanan wouldn't speculate on just how many others might be involved.

"But it just strikes me - especially in light of what Newshub is doing now with the larger white supremacist community - I mean the fact that that guy supposedly acted completely alone amidst this other crowd strikes me as a little incongruous, to say the least."

Paul Buchanan.
Paul Buchanan. Photo credit: The AM Show

Since the September 11, 2001 attacks, Dr Buchanan said there has been too much focus on suspects' faith and appearance.

"Wash out the colour and just focus on behaviour - there is the solution to the problem," he explained.

"If it was known that white supremacists existed... and if it was known that some of these had violent tendencies and had a penchant for collecting arms, then I would have thought - given that police and intelligence agencies have been looking at animal rights activists and environmental activists that they would have said you know, 'That combination of extremist ideology and weapons is not a good one. Maybe we want to go over there and have a look.'"

While security agencies the GCSB and SIS have been criticised for failing to pick up growing white supremacist activity, Dr Buchanan said the alleged Christchurch killer - despite his social media activity - might still have flown under their radars.

"Most of what Five Eyes does is state-on-state espionage - the old-fashioned stuff... Without a tip, without an informant, it would have been very hard for a signals agency like the GCSB to start wire-tapping the killer, in this instance."

Prime Minister Jacinda Ardern is presently in France, hosting a summit with world leaders and tech bosses on how to handle the growing use of social media to spread terror and hate.