It has been quite common in Mexico for criminal organizations to engage in pre-election violence at the municipal level as influence over local power is crucial to their business and much easier to hold than at a state or federal level. This was their latest — but certainly not their last — attempt to get their preferred candidate elected.
While there is indeed a correlation between gang violence and political violence in some Mexican states, this oversimplification fails to explain how political violence can be high despite relatively low levels of gang-related crimes. Power dynamics and local-level disputes also contribute to this worrisome trend.