Nemesio Oseguera Cervantes
On 27 September 2011, Mexico's Office of the General Prosecutor (PGR) issued an arrest warrant for El Mencho and offered MXN$2 million for anyone who can help provide information that leads to his arrest. He was accused of organized crime involvement and illegal possession of firearms. In March 2014, the United States District Court for the District of Columbia, based on the previous investigations by the DEA, indicted El Mencho for several charges, including drug trafficking and for being leaders of a "Continuing Criminal Enterprise". El Mencho and Abigael were accused of coordinating shipments of cocaine and methamphetamine from South America via Mexico to the U.S. They also stated that the CJNG and Los Cuinis coordinated the collection and delivery of the drug proceeds from the U.S. to Mexico. In addition, the United States District Court for the Western District of Texas is looking to convict El Mencho for drug trafficking offenses.
2015 San Sebastián del Oeste ambush
The month before the ambush, on 19 March 2015, the CJNG attacked a convoy of the National Gendarmerie (), a branch of the PF, in Ocotlán, Jalisco. 11 people were killed; 5 of them were police officers. The attacks were part of a larger campaign by the CJNG to avenge the capture or deaths of its leaders. Investigators believe that the attacks were masterminded by Nemesio Oseguera Cervantes (alias "El Mencho"), the top leader of the CJNG and one of Mexico's most-wanted drug lords. The intention of the attacks was to avenge their fallen comrades and show the government their manpower to strike back. On 23 May 2015, El Gringo and his suspected henchmen were driving through Zacoalco de Torres, Jalisco, when they encountered the Jalisco State Police. The CJNG members tried to escape, but their vehicle turned over as they sped away from the police units. Two gunmen opened fire at the police officers and threw a grenade at them. 
However, the police was able to neutralize the aggression and kill 4 of them, including El Gringo. One policeman was wounded in the attack; he was shot in the leg and calf, but was reported in stable condition. At the time of his death, El Gringo was suspected by law enforcement to be the regional leader of the CJNG in Zocalco de Torres and other municipalities of the region. There were 10 pending investigations against him, and he was suspected to be involved in gas theft, kidnappings, and in at least nine homicides. They also believed that he was responsible for a number of attacks against law enforcement, including the gunfight that left 4 Mexican Army soldiers dead on 12 May 2014 in Guachinango, Jalisco, and the murder of two police investigators in Tlajomulco de Zúñiga, Jalisco on 29 July 2014. According to investigators, El Mencho reportedly ordered the CJNG to carry out attacks against the government security forces in Jalisco as retaliation for El Gringo's death.