LIFE.com recalls a killing spree from a half-century ago: The story of the American mass murderer Billy “Cockeyed” Cook — who killed six people, including an entire family of five, during a terrifying three-week spree across several American states in early January 1951. It’s a reminder that the unspeakable and the sensational frequently go hand in hand, and that the lessons we glean from such savagery are, all too often, quickly forgotten.
See the photos here.

