Should New Zealand's security agencies have known about the mosque murderer, and why didn't they?
Prime Minister Jacinda Ardern has been asked those questions several times. She has replied that the public deserves answers, and will get them when the inquiry into the killing of 50 Muslim worshippers has completed its work.
The Security Intelligence Service and the Government Communications Security Bureau are the guardians off the nation's safety, and they will have some serious questions to answer.
What is known is that Brenton Tarrant, arrested 21 minutes after police received the first triple one call and now charged with murder, wasn't on the security radar in Australia or New Zealand.
He is an Australian citizen but spent most of his time in recent years in other countries.
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Justice Minister Andrew Little, who is responsible for the SIS and the GCSB, says the inquiry will assess what they should have known and what they could have known.
He signs all the surveillance warrants, and doesn't accept that their focus has been skewed towards Islamic extremism at the cost of far-right nationalism.
"A proportion (of the warrants) relate to extremism, all forms of extremism," he said.
GCSB director. Andrew Hampton, in a rare public comment, confirmed that no relevant intelligence was collected on Tarrant, nor was any received from the bureau's Five Eyes partners Australia, Canada, the US and Britain.
He also said the GCSB didn't have the legal authority or the technical means to monitor all online activity.
It has been reported that Tarrant took part in far-right chat rooms, but it seems he didn't say or do anything sufficiently serious for anyone to take notice.
