I'm assuming all guns were 'legal' at some point, unless it's some weird home-made contraption. Not sure what percentage of gun crime is committed using weapons purchased in other jurisdictions and illegally imported.
The Christchurch nutter bought his guns legally, and surprise surprise it was the good old AR-15 type weapon once again:
A Christchurch gun shop on Monday acknowledged selling guns online to the 28-year-old white supremacist accused of killing 50 people in mosque shootings that have upturned New Zealand’s reputation as among the world’s most tolerant and safe nations.
www.washingtontimes.com
Doubtful he could have done what he did if in Australia.