Not sure, but I think gun laws are slack in NZI wouldnt have been shocked. With the rise of Alt right ethnic nationalists such as yourself, it was only a matter of time. RWNJ's are fundamentally dominated by the 'angry disenfranchised white men with a fixation for guns who hate everyone who's different to them' who spend an awful amount of time on the internet talking politics on social media.
That's kind of the prime 'mass shooter demographic' right there.
Add to that the fact their far right wing doctrine encourages hatred, conflict and persecution of minorities and it's only a matter of time.
We've had massive Right wing terrorist attacks in the USA, Canada, UK and now NZ. Right wing terrorists are a close second in terrorism related attacks behind Islamists.
I'm only shocked it hasnt happened here in Oz yet.
(Which it almost ******* did, going by the fact the perp was Australian).