Overview: In 2017, Alexandre Bissonnette went into a mosque in Quebec City and gunned down six people. Is he a lone-wolf terrorist or a mentally-ill young man turned monster? In the documentary Dear Mr. Bissonnette, Mark Kelley investigates the path of a killer using the people closest to him and real life Mindhunter profilers, to discover mass shooters like Bissonnette are always hidden in plain sight.