Isa Mazzei is a writer and filmmaker best known for Blumhouse’s hit “Cam” and Neon’s “How to Blow Up a Pipeline.” Her memoir “Camgirl” was named one of NPR’s “books we love.” She is co-writer and executive producer on the just-released “ Faces of Death ” from IFC Films. Here, Mazzei shares the essay “Tetris,” one she penned about millennials, the advent of digital violence and what it means to be a spectator to trauma. – Matt Donnelly The man bleeds out slowly, a metal fence jutting through his