Each year the FBI estimates between 25 to 50 active serial killers hunt their prey in America, taking the lives of hundreds of innocent people annually. Often these killings keep a city on edge, a heavy fear permeating the night air before these predators are taken off our streets. Just ask those who lived through the terror of The Night Stalker, Son of Sam or The Grim Sleeper. And years later the public still can't seem to get enough of their stories which continue to be retold in documentaries and limited series.