Nemesio Oseguera Cervantes
According to the Mexican government, El Mencho may be hiding in the state of Jalisco, the CJNG's stronghold. However, they believe he does not stay in one place for too long, and travels across several municipalities in Jalisco and into the states of Michoacán, Colima, and Nayarit. He usually travels across the mountains and rural terrains in these areas since it provides multiple escape routes in the event that security forces attempt to encircle him. Authorities suspect El Mencho's inner circle is made up of mercenaries with former military training. His second security circle is much larger in size and serves as a rearguard to notify El Mencho's inner circle of suspicious activity and ambush potential parties that attempt to get close to him.
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.