Law enforcement and the newspapers had long posed the question as to whether Zodiac had any involvement in the brutal stabbing murders of the two young San Jose girls. The two teenagers, Debra Gaye Furlong (14) and Kathy Ann Snoozy (15), had been savagely attacked with a short-bladed knife on August 3rd 1969. Therefore, it didn't come as much of a surprise when the Zodiac Killer bolstered his victim total to seven murders on November 8th 1969, when he mailed the 'Dripping Pen Card' to the San Francisco Chronicle. After the attack on Cecelia Shepard and Bryan Hartnell at Lake Berryessa, followed by the message on the car door, a depiction of a fountain pen dripping with blood probably seemed like an apt choice by the Zodiac Killer.
I couldn't help noticing the similarities between the Dripping Pen and Dripping Knife of Zodiac, particularly because of the seven blood drops falling from the knife correlating with his "I've Killed Seven" claims in the greeting card and the addition of "Aug" in his chronological victim count. We know he was responsible for five murders, that of David Faraday, Betty Lou Jensen, Darlene Ferrin, Cecelia Shepard and Paul Stine - but had now tagged victims six and seven onto his running total. These two extra victims were Debra Furlong and Kathy Snoozy.
Five weeks later, on December 16th 1969, he effectively rejoiced in these murders by mailing the "The Bleeding Knife of Zodiac" correspondence, which depicted seven drops of blood falling from a knife - one for each victim - and fashioned like his Dripping Pen card. The Zodiac Killer, inspired by the Deborah Furlong and Kathy Snoozy murders on August 3rd 1969 and its coverage on the front page of the Chronicle three days later, launched his callous knife attack at Lake Berryessa seven weeks later, resulting in the premature death of Cecelia Shepard. The Zodiac Killer was hoping the attack on the shores of Lake Berryessa would augment the belief of law enforcement to his involvement in the San Jose murders. This is why he wrote August on the Dripping Pen card, bumped his total up to seven and then boldly exhibited the "The Bleeding Knife of Zodiac" on December 16th 1969 with seven drops of blood.
The drawing of a 'bleeding knife' not a direct reference to the "by knife" phrase written on the car door of Bryan Hartnell at Lake Berryessa, but more of a triumphant claim of his involvement in two brutal knife attacks in the Bay Area. It would take nearly two years to conclusively expose this deception, coming with the arrest of Karl Francis Werner in late April of 1971. Regardless, the Zodiac Killer wasn't finished yet.