As Zelms and his parter Don Fouke were driving towards the murder scene, they encountered a lone caucasian male walking away from the direction of the crime scene. Zelms was one of two SFPD officers who likely saw and possibly spoke to the infamous Zodiac Killer on the night of October 11, 1969, as they responded to the Zodiac Killer's murder of cab driver Paul Stine in the Presidio Heights area of San Francisco.
In the opening, when the memorial wall with the names of SFPD officers killed in the line of duty is shown, the name 'Eric A Zelms' is shown.
