A series of murders targeting families, including children, has rocked Mexico in recent weeks, signalling that drug gangs are willing to break an unspoken code of honour within the criminal underworld.
In total, 34 people have been killed, including several women and 10 children, since early July in three regions.
Last month, 19 people, including eight children, from three different families were gunned down in less than a week in Ciudad Victoria, the capital of the northeastern state of Tamaulipas.
Authorities suspect that those massacres were linked to disputes between rival gangs in Tamaulipas, a region that has been besieged by drug cartel violence for years.
On July 18, seven shark fishermen from the same family were killed in the southern Pacific coast state of Oaxaca.
Authorities suspect it may be linked to illegal activities at sea. The Pacific is a key route for drug trafficking.
The most recent massacre came on Saturday, when seven people from the same family, including two children, were shot dead in a small town in southern Guerrero state.
While the motive is unknown, gangs are fighting for control of opium poppy production in the region.
Code is finished
The modus operandi indicates that all these killings were linked to turf wars between criminal organizations that are the remnants of cartels that have splintered, said Raul Benitez Manaut, a security expert at the National Autonomous University of Mexico (UNAM).
Such gangs "no longer respect families, wives, and children," Benitez Manaut said.
A police agent investigating the slaughters in Tamaulipas said there used to be "a code of honor in which family was untouchable" in the old days of large cartels led by veteran capo.
"Now, in these modern times, this code is finished," said the agent, who spoke on condition of anonymity because he is not authorized to speak publicly.
The Gulf and Zetas drug cartels have been fighting in Tamaulipas for years, but several of their leaders have been arrested or killed. Violence in Ciudad Victoria is blamed on offshoots of the Zetas known as the Old School and the Cartel of the Northeast.
Experts warn that the vendettas between criminal cells may rise as family killings continue.
Mexico's paltry record at putting criminals behind bars encourages gangs to kill without fear of consequences, analysts said.
Only one per cent of crimes in Mexico lead to convictions, according to a 2016 study by the University of the Americas in Puebla state.
The spate of family killings "is more evidence of the impunity and lack of coordination to deal with or contain crime," said Javier Oliva, another prominent security expert at UNAM.
"You can murder entire groups, including minors and women, without getting justice immediately," Oliva said.
Alejandro Hope, a former official at Mexico's CISEN intelligence agency, said a gang "doesn't run more risks killing one person or eight or 11 people" as investigations are not rigorous and special operations are lacking.
Such acts of "extreme brutality" will continue as long as they carry little risks for criminals, Hope said.
While killing women and children can spark revenge attacks, Hope said there are grim advantages for the killers.
Killing a rival's son eliminates a potential competitor in the future, gets rid of witnesses and intimidates the enemy, he said.
It also fuels fear among civilians and the authorities, discouraging people from reporting crimes, the expert said.
The Tamaulipas police agent blamed the spate of family murders on the nefarious influence of Central American gangs that have worked with Mexican drug cartels.
"When Mexican cartels saw that they didn't have enough heartless people to finish off their enemies, they began to bring the Mara Salvatrucha (gangsters) from El Salvador, who are known internationally for their savagery," the agent said.
"It's not because impunity allows it," he said. "It's because these are people who are brought from outside with this type of criminal ideology."