In compliance with the wishes of the San Francisco Police Department, the Chronicle withheld the threat on a school bus when this latest Zodiac letter was published in the newspaper on October 15th 1969. It wasn't until October 17th 1969 that the Chronicle published the threat on a school bus. Therefore, the threat delivered by telephone to Santa Rosa by somebody claiming to be the Zodiac Killer on October 15th 1969, promising to blow up a school bus, was made before the Zodiac Killer's threat in his letter was ever released in the newspapers. This suggests it was the Zodiac Killer who telephoned the school bus threat in Santa Rosa on October 15th 1969. This is what was reported in the Chronicle on October 21st 1969: "Someone hinting he might be Zodiac has telephoned such a threat in Santa Rosa. The man responsible for the safety of the students who ride the buses is Fred Sowash, the district's transportation director. Since last Wednesday, when he learned of Zodiac's threat, Sowash has been devoting 18 to 20 hours a day to blunt it". Last Wednesday was October 15th.
On October 17th 1969, a female school bus driver was traveling southeast towards Yulupa Elementary School in the morning, when she claimed she heard a shot ring out, stating "As I came around this bend I heard a loud shot from the left hand side of the bus. The children heard it too. Now I don't know if anything struck the bus. We can't find anything that struck the bus". Looking at the October 17th 1969 KRON News footage, it appears she may have been traveling along Bennett Valley Road in Santa Rosa, with relatively low density housing dotting the route and the Sanoma Mountains in the distance. This route would have provided the perfect cover for the Zodiac Killer to shoot out the tires of a school bus in relative seclusion. Assuming a shot was fired at the bus and heard by the driver and/or schoolchildren, either he missed, or his intention was merely to create panic on the school bus to ensure the shots were heard and reported - and thus lend credibility to his telephone threat two days earlier. After the shot, the woman driver "hit the foot feed and started going on", realizing there were no other cars in the vicinity she could get the attention of. "So I just kept going fast to the Yulupa School" she added.