“It’s obvious, in the context of violence or criminality, it doesn’t happen without the collaboration or the permission of agents of the state,” said Luis Efrén Ríos, director of the law school at the Autonomous University of Coahuila and a member of the official working group on the disappeared. “It’s up to the prosecutor to determine who is responsible.”

Questions about possible government complicity — directly or indirectly — generally dissipate when violence is branded as Zeta-related. Indeed, as violence in Mexico’s northern region continues unabated, in lieu of investigations and convictions, Zeta is the catchall explanation applied to criminality, one that has the effect of silencing further questions.

But a closer look at the details of the massacre, the government operation, and documented disappearances by human rights groups offers a glimpse at network of corruption, collusion and impunity concealed behind the letter Z.

“It’s more than Zetas against Zetas. It has to do with corruption. It has to do with political power,” said Guadalupe Correa-Cabrera, chairwoman of the government department at the University of Texas at Brownsville and author of a forthcoming book about the Zetas. “There exist elements that suggest the use of paramilitary tactics, in which it’s not clear the role of the state in clashes and mass executions.”

A massive unmarked grave

People began to disappear in Mexico in large numbers after President Felipe Calderón launched his war against drug traffickers in 2006. By 2013, the Mexican government, under a new administration, pegged the number of disappeared at 26,121, adding that not all were criminally related.

Experts and several human rights groups, however, estimate that reported cases represent roughly 10 percent of the total, as most people are reluctant to appeal to authorities who were either involved in or suspected of having ties to organized crime groups. Based on their calculations, the actual number could be closer to 200,000 people.

Disappearances carried out by organized crime groups were generally motivated by the possibility of obtaining a ransom, said former journalist Raymundo Ramos, now the director of the Human Rights Committee of Nuevo Laredo. In the case of authorities, he said, the navy would detain people after receiving information that the person was tied to organized crime or drug or arms trafficking.

“Those who cooperated — meaning they had information that would help the military identify people involved in organized crime — were released,” he said. “When these people were released, the first thing they did was leave the city.” Others, he said, were never heard from again.

From May through July of 2011, Ramos calculated, the navy detained approximately 80 people just in Nuevo Laredo. One of them was Jose Cruz Diaz, a tattoo shop owner. In June 2011 a navy convoy arrived at Cruz’s tattoo parlor in central Nuevo Laredo and, according to his wife, Barbara Peña, began searching the premises.

She said the uniformed men didn’t ask for anyone in particular and didn’t present a court order. After a few minutes, they found a small quantity of marijuana and detained Cruz and another man.

“They were pleasant,” Peña said. “They even let him leave the keys to the shop and someone in charge.”

In a press release, the navy admitted it had been in contact with Cruz. “Up to the present, there is no evidence that suggests that navy personnel secured, much less unlawfully deprived these persons of their liberty.”

Cruz was never seen again.

On May 15, 2014, three months after Ramos spoke with Al Jazeera America, some 50 armed members of the navy surrounded the Human Rights Committee of Nuevo Laredo’s offices. He said they attempted to enter and search to “ensure everything was in order.” Human Rights Watch issued a letter to the Mexican government expressing alarm and requesting intervention. After searching nearby homes, the navy cleared the area.

A sack of corruption

On the patio of his residence in Coahuila, Bishop Raul Vera explained the outbreak in violence and disappearances like those in Allende by invoking a memory from his childhood. He described slipping into the church confessional booth and with each misdeed he uttered, Vera imagined frogs, snakes and cockroaches springing from his mouth.

“Well, that’s how I see the image of the Mexican state — with a sack in which there are all sorts of roaches, all kinds of corruption. You try and clean it out, but the sack is so deep.”

There comes a moment, he says, when you can’t dive any deeper because inside lie monsters that are very powerful.

“Let’s suppose that there had existed a small, tenuous difference between the supposed legal and political system and the narco organizations, the cartels,” said Vera, who operates the Center for Human Rights Fray Juan de Larios, which defends migrants’ and prisoners’ rights. “That line is faded now because of the degree of corruption.”