I can't claim to understand the situation in Mexico, but many of the stories I have raid make it clear that corruption and brutality are facets of everyday life, be it from the government or from the cartels. It'd be one thing if this was an isolated incident, but it doesn't seem to be, and the state doesn't seem too interested in outing everybody involved. What can you even do in a situation like that outside of being prepared to lose a lot of lives to make lasting change.
Have a friend who grew up in Mexico - dad was a Swiss national, mom Mexican, dad left when she was 6. Led an archetypal Mexico City life - dirt floor but fridge, etc. Did sound for Vincente Fox's campaign. Things were a basic "trade stories of rural poverty" game until she mentioned that her husband had been kidnapped by Narcos twice. Robert Kaplan made a run at comparing northern Mexico to northern Afghanistan from a geopolitical standpoint. It's a mountainous region where criminal gangs, once they get established, become pernicious and difficult to uproot. That book was worth it for that point alone - that once you get an outside perspective, there isn't too much difference between Waziristan and Chihuahua.