The bodies of a man and woman were found hanging from a bridge in Nuevo Laredo, a border town in Mexico.
Signs by the bodies said that the two had denounced a cartel on Twitter.
Drug violence is common along the U.S.-Mexico border as cartels clash over territory, and the cartels have always been intolerant of anyone who stands in their way. Journalists have been targeted and killed for reporting on the cartels, and many who still work in cartel territory choose to self-censor to avoid harassment or worse.
But with the rise of social media, Mexicans have gone online to voice their discontent. They blog and Tweet about the cartels and the violence they experience, mostly anonymously for their own protection.
The cartels, it seems, are now lashing out even against them.
The sign left with the bodies, according to CNN, said:
"This is going to happen to all of those posting funny things on the internet," one of the messages said. "You better (expletive) pay attention. I'm about to get you."
The note was signed 'Z', a likely reference to the Zetas cartel, which has a foothold in the area and is one of the most powerful cartels in Mexico.
The bodies were mutilated and showed signs of torture. No one has yet claimed them, and they haven't been identified.
It's a disturbing mark of the reach of cartels, which have come to kill with impunity, particularly in the border region, as well as their clear aim to cow an entire population with strategic — and horrific — acts of violence. Their message these days is that anyone could become their next victim.
But it's unclear how long that strategy will work. Fed up with violence, Mexicans have taken to the streets this year in increasing numbers.
They erupted in outrage after a recent attack in Monterrey, when 52 civilians were killed after gunmen — likely Zetas members, police said — torched a casino that hadn't paid the cartel a sufficient bribe.
It's even more difficult to stifle dissent online, where many people comment anonymously. As one defiant Twitterer noted in Spanish:
"Enough! If we shut up today, we will have lost the ground that we have gained. This is the time to show what we are made of."