Extreme right-wing terrorism, mostly of the "white nationalist" variety, is becoming as big a problem as Islamist terrorism in many places. That's certainly the case in the United States, where the U.S. Government Accounting Office calculated last year that 119 Americans have been killed by Islamist extremists since the 9/11 attacks, and 106 Americans by far-right extremists.
It's also true that almost all the attacks are designed to exploit social media. Brenton Tarrant, the suspect in the New Zealand mosque attacks, had a number of semi-automatic rifles with him in Christchurch, but his real weapon was the GoPro camera on his headband live-streaming his atrocities.
All too common in the world, but I was still astounded when I heard that such a huge terrorist attack had happened in New Zealand. Fifty murdered in two mosques! This is a country of over 4 million people where there were only 35 homicides in all of last year. Then I heard that the terrorist was an Australian, and it made a bit more sense.