What Was The New York Zodiac Killer's Calling Card?

Forensic psychologist Dr. Joni Johnston discusses the signature mark of the New York Zodiac killer Heriberto Seda. "He picks his victims based on their astrological sign ... It almost seems as if he is trying to find some almost random way to feel special or to fit his needs and his desires into some kind of acceptable or understandable framework," Dr. Johnston says.