Zodiac Killer Bus Bomb Threat Letters 1969

In late 1969, the Zodiac Killer escalated his threats through letters describing plans to bomb school buses. These communications demonstrated an increased desire to create mass fear beyond individual attacks. The threats significantly heightened public anxiety and forced authorities to consider broader protective measures.

Not applicable.

Authorities analyzed the letters and attempted to verify the legitimacy of the threats. Increased police presence around schools was implemented as a precaution.