The brewing conflict between aspirants to the Sinaloa cartel throne apparently reached a new stage earlier this month, when gunmen aligned with one cartel leader attacked the sons and a longtime associate of jailed kingpin Joaquín "El Chapo" Guzmán.
According to a letter purportedly handwritten by Jesús Alfredo and Iván Archivaldo Guzmán, the attack occurred when they, with Ismael "El Mayo" Zambada, arrived at a February 4 meeting called by longtime cartel member Dámaso Lopez "on the issue of having evidence that Dámaso López ordered the kidnapping of the sons of 'El Chapo,'" which took place in August.
Upon their arrival at the meeting site — reportedly in Badiraguato, the Sinaloa municipality where "El Chapo" Guzmán was born — gunmen opened fire on them. According to the letter, which was originally published by Mexican journalist Ciro Gómez Leyva, some of the bodyguards were killed instantly.
At that point, according to the letter, the brothers "realized they were betrayed by el licenciado Dámaso López, trying to kill them and end completely" the Guzmán family line, the letter states, referring to López as "licenciado" in reference to his law degree.
"This in fact did happen," Mike Vigil, a former chief of international operations for the US Drug Enforcement Administration, told Business Insider, citing conversations he had with Mexican security officials.
"Apparently [Dámaso López] called for an important meeting, and when they showed up they ran into a barrage of bullets from at least five or six or individuals," Vigil said. "They killed some of their bodyguards, but they were able to [get] away."
The Guzmán sons and Zambada fled the scene, but encountered other armed men with orders from López to kill them. The letter says they traveled several kilometers before finding a small town where they received aid for the wounds they sustained, though it's not clear if "El Mayo" Zambada was wounded.
"Apparently [the gunmen] didn't wait for these guys to get out of the vehicle when they started shooting," said Vigil, author of "Metal Coffins: The Blood Alliance Cartel."
"Had they waited until they got out of the vehicle, they would've probably killed them," he added.
José Refugio, a Mexican lawyer who represents "El Chapo" Guzmán, acknowledged the letter in an interview with Mexico's Radio Formula.
"I had knowledge of this. I knew of that letter, and I knew they made that letter" he said. "But it did not arrive through me."
The Dámaso López referenced in the letter appears to be Dámaso López Nuñez, a high-level leader for the Sinaloa cartel who was rumored to be Guzmán’s successor after his arrest in February 2014.
López Nuñez, originally from Sinaloa state, was a police officer in that state and later deputy director for security at Puente Grande prison in Jalisco state when "El Chapo" Guzmán was there in the 1990s and aided the kingpin's escape in 2001.
"He's a former police officer, and he's also an attorney, and he's got a son that ... they call him 'Mini Lic,' or 'Mini licenciado,' or 'Mini Attorney,' who apparently also is tied to the Sinaloa cartel [and] apparently works out of Baja California Sur," Vigil said.
In 2013, the US Treasury identified López Nuñez as a principal lieutenant of the Sinaloa cartel, because of his alleged role the cartel's drug trafficking and money laundering activities.
Because of his law degree, López Nuñez is nicknamed "El Licenciado."
The letter refers to him as such, suggesting he was in fact behind the attack. However, some reports of the incident cite "El Mini Lic" — López Nuñez's son, Dámaso López Serrano — as the culprit. The younger López, 37 years old, is reportedly the founder of Los Antrax, an armed wing of the Sinaloa cartel.
López Nuñez is the son of Dámaso López García, who was a member of the Institutional Revolutionary Party in Sinaloa. The PRI is also the party Mexico's current president, Enrique Peña Nieto.
The link between the López family and the PRI has added to suspicions that the party is currently tied to drug trafficking — a belief bolstered by the party's involvement with the drug trade in the latter half of the 20th century, when it governed Mexico as a de facto one-party state.
The attack on the Guzmán sons and "El Mayo" Zambada comes amid a spike in violence in Sinaloa state, which has picked up in the months since the elder Guzmán's extradition in late January.
There were 12 people were killed in the state over the weekend, with four people killed in Culiacan in two shootings just 40 minutes apart.
In 72 hours between Sunday and Tuesday, 13 more people were slain in five shootouts between criminal groups.
The state's public security secretary, Gen. Genaro Robles Casillas, told news agency EFE that the wave of violence was the result of fighting between factions of the Sinaloa cartel for control of the territory.
"There's been a rash of killings in Culiacan," the state capital, Vigil told Business Insider on Thursday. "I think there were quite a few murders. They estimate about 30 to 60 murders that have happened there in the last couple of days."
"El Chapo" Guzmán's sons also distributed a letter in October, denying their involvement in a roadside ambush in Culiacan, in which five soldier were killed and several injured.
That attack was initial thought to be an effort to liberate a captured cartel member, but it is now suspected that one cartel faction launched in in order to attract law-enforcement attention to territory controlled by a rival faction.
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