A letter left with the cartel gunmen, who had been trussed up and left on the roadside, accused them of acting "under their own decision-making and lack of discipline" as well as supposedly breaking cartel rules over "protecting the lives of the innocent".

It was signed by the "Scorpions Group", a splinter faction of the powerful Gulf Cartel.

The letter points to the strange, misplaced sense of civic duty which many Mexican cartels claim to possess. Despite the widespread fear they sow through extortion, murder and kidnapping, groups like the Gulf Cartel and their rivals, the Sinaloa Cartel, profess a twisted code of ethics under which they believe they are looking out for the most vulnerable in Mexican society.

That warped understanding of compassion and altruism does not extend to undocumented migrants, who are routinely kidnapped, raped and murdered. Nor are local businesses exempt from paying "el piso", an extortion for merely operating on their territory, the tax applied to everyone from multinational companies to small, family-run convenience stores.

Yet, there is a logic to the cartel's code of behaviour, particularly in remote and rural parts of Mexico and poor mountainous communities, where organised crime often fills the role left by the state.

One need only look at their response after natural disasters. When hurricanes or earthquakes hit the western state of Guerrero, criminal gangs distributed emergency supplies and bags of food, even stamped with their cartel's distinctive initials. A similar phenomenon was seen during the worst moments of the Covid lockdowns too.

The cartels also consider themselves the maintainers of community order, handing out brutal summary justice to child rapists or thieves who operate outside their purview. They are the judge, jury and executioners, often quite literally.

In that context, the decision to hand over their own gunmen after the debacle in Matamoros adds up: A mistake happened, an apology was made, and the culprits handed in. Case closed.

And even Mexican drug cartels are aware of the power of good PR.

That sense of neatly curtailing the chaos while apologising to the city's residents must also be taken with a huge pinch of salt, however.

How can one be sure these five men were the perpetrators? Who can be trusted to be telling the truth? The drug cartel? The state Attorney General's office? In waters as murky and muddied as those of Tamaulipas state, the wisest instinct is generally to question anything one is told.

Lest we forget, Mexico's former Public Security Secretary, Genaro Garcia Luna, who was once the highest official in law enforcement and the man who led the war against drugs, is currently languishing in a US prison having been found guilty of working alongside the Sinaloa Cartel in exchange for millions of dollars in bribes.

In the Matamoros case, authorities in Mexico have been highlighting the victims' criminal records in their statements to the media.

We were initially told the Americans were in town for health tourism - a cheap Mexican tummy tuck that went about as badly wrong as possible.

A day later, as allegations began to swirl, a member of the Mexican government forwarded me a story about the victims' criminal past, specifically that one had a conviction for manufacturing illegal narcotics with an intent to supply.

"Just checking you'd seen this", went the innocuous comment.

Whether that was part of a concerted push in Mexico to victim-blame or because there is hard evidence to suggest the kidnapping was targeted is again hard to know.

One thing that the entire mess has reminded me of was one of my own trips to Tamaulipas shortly after arriving in Mexico in 2011. It taught me something critical about the drug war in Mexico which has stayed with me to this day.

In a non-descript hotel room, I met the girlfriend of a member of the Zetas, a particularly bloodthirsty cartel which today is largely disbanded. As we filmed her in the shadows, her name changed and her voice disguised, she described what her boyfriend did. Without naming the exact organisation, it was clear he worked in law enforcement yet was also a member of the Zetas.

A cop by day, a narco by night.

"What you're telling me", I asked naively, "is that the relationship between the cartels and the state is very close?"

"No", came her chilling reply, "I'm saying the cartels are the state."