
The murder of taxi driver Paul Stine marked a significant escalation, as the Zodiac Killer committed a killing in an urban environment. The crime demonstrated boldness and increased risk-taking. The killer also took items from the victim as proof for later communication.
The Zodiac shot Stine in the head, removed part of his shirt, and fled the scene. The act of taking evidence was used to authenticate later letters.
Witnesses observed the suspect leaving the scene. Evidence linked the crime to Zodiac through subsequent letters.