A.C. Thompson, Lucas Waldron & Christopher Mathias
A.C. Thompson is a staff reporter with ProPublica. Lucas Waldron is ProPublica's visual investigations producer. Christopher Mathias is a national reporter at HuffPost, based in New York City.
In recent months, YouTube has emerged as something of a flourishing option for white supremacist and neo-Nazi videos—spreading ideas cited by the alleged New Zealand mosque gunman.