The #ZodiacKiller or simply Zodiac is the pseudonym of an unidentified American serial killer who operated in Northern California from at least the late 1960s to the early 1970s. The killer originated the name in a series of taunting letters and cards sent to the local Bay Area press. Wikipedia  

Dennis Lynn Rader is an American serial killer known as BTK or the #BTK Strangler. Rader gave himself the name "BTK". Between 1974 and 1991, Rader killed ten people in the Wichita, Kansas metro area. Rader sent taunting letters to police and newspapers describing the details of his crimes. Wikipedia #DennisRader