The terror attack in the New Zealand city of Christchurch appalled the world. The indiscriminate shooting of 50 Muslim worshippers during Friday prayers was calculated to spread fear and a message of right-wing terror. The plot was intricately planned, harnessing the tools and the power of the internet, to amplify the terror to a global audience. On Monday, Four Corners investigates how the Australian born accused killer was able to operate under the radar.