Aristoteles Sandoval was shot dead in a restaurant toilet in the early hours of Friday.
Mexican authorities said they have found 19 shot and burned bodies near a town across the Rio Grande from the US state of Texas in an area that has seen violent territorial disputes between organised crime groups in recent years.
The Tamaulipas state prosecutor’s office said late on Saturday that the bodies were discovered along a dirt road outside Camargo after residents reported a burning vehicle.
Authorities found two vehicles on fire, containing the remains of 19 victims. Some rifles were also found.
All 19 victims had been shot, but shells were not found at the site, leading investigators to believe they were killed somewhere else.
“In one of the vans there were two bodies in the front seats, another body on the side of the driver’s door, one more on the side of the passenger door and 15 bodies in the back of the vehicle,” a statement by the state police read.
“Initial investigations show that death was caused by firearm projectiles and then [the victims] were set on fire,” it added.
A Camargo official, who requested anonymity due to security concerns, said the killings occurred on Friday, but people had been afraid to report them.
A separate source from the prosecutor’s office told AFP news agency that an investigation has been launched to determine whether the victims were undocumented migrants, as some local media have reported.
The official said they have contacted Guatemalan consular authorities in Mexico “to provide the necessary information and try to identify some of the people believed to be Guatemalan migrants.”
Camargo, a town of about 15,000 people, borders Texas and the Mexican state of Nuevo Leon.
Authorities from Nuevo Leon are cooperating with the Tamaulipas prosecutor’s office.
The region sees frequent clashes between the Noreste cartel, which controls a part of Nuevo Leon, and the Gulf cartel, which has been active in Tamaulipas for decades.
In January 2019, in the Tamaulipas town of Miguel Aleman, 24 corpses were found, 15 of which were charred.
In August 2010, a group of 72 undocumented migrants were killed in San Fernando, Tamaulipas. Authorities said the massacre was perpetrated by the Zetas cartel, one of the most powerful at the time.
Tamaulipas, on Mexico’s Gulf coast, is the shortest route to the US but also the most dangerous because of the presence of criminal gangs, which kidnap, extort and murder migrants.
Mexico recorded 34,523 assassinations in 2020, a slight decrease on 2019’s figure of 34,608, which was a record high since official tallies started.
Cartel-related violence has beset Mexico since 2006, with more than 300,000 killings since then.