morf, you are correct. The police were seeking a black man in connection with the murders of Michael Shain and Cathy Pethtel on December 3, 1973.
Sandy and I have been to the crime scene which is at Interstate 580 by Pleasanton. It is open to speculation whether or not these murders were linked to the Zodiac because the Zodiac mailed a letter from Pleasanton on March 13, 1971.