It's not really the police who killed the tiger: It's whoever's responsible for it getting loose. Ultimately, it is the zoo. Next, it's whoever designed the methods by which tigers are locked in. Next, it's whoever developed the quality assurance plan for that process. Then it's whoever was responsible for managing the implementation of the plans and processes. Then it's whoever was supposed to be implementing the lockdown process and QA procedures.
When something goes this wrong, there are usually multiple failures. Actually, by definition when something goes this wrong there are multiple failures (if a system can fail catastrophically from a single failure, then the system design is a second failure (and the most serious one).