Mexican security forces killed Nemesio Oseguera Cervantes, known as 'El Mencho,' the leader of the powerful Jalisco New Generation Cartel (CJNG), during a military operation in Tapalpa, Jalisco, on Sunday.

The operation, carried out by the Mexican Army at dawn, resulted in Oseguera's death, according to government sources and local media reports. Officials confirmed the killing, though Mexico's security minister did not immediately comment publicly.

Born in 1966 in Aguililla, Michoacán, Oseguera rose from guarding marijuana fields as a teenager to leading one of Mexico's most dominant cartels. Deported from the U.S. in the 1990s after drug-related arrests, he joined the Milenio Cartel before founding the CJNG around 2010 following internal splits.

Under his command, the CJNG expanded nationwide and internationally, trafficking methamphetamine, fentanyl, cocaine, and heroin while engaging in extortion, murders, and attacks on security forces. The cartel, based in Jalisco—home to Guadalajara and Puerto Vallarta—rivaled the Sinaloa Cartel in violence and reach, with estimated assets of $50 billion.

The U.S. had offered a $15 million reward for his capture, while Mexico posted 300 million pesos. Oseguera evaded multiple raids, including a 2015 operation that downed a military helicopter and killed nine soldiers.

News of his death sparked immediate retaliation. Videos showed gunmen setting vehicles ablaze and blocking highways in Jalisco, Michoacán, and at least five other states. Jalisco Governor Pablo Lemus Navarro urged residents to stay home amid clashes, while public transport was suspended in parts of the state.

Airports in Guadalajara and Puerto Vallarta saw flight disruptions, and hotels were told to keep guests inside. The U.S. Embassy issued a shelter-in-place alert for Americans in Jalisco, Tamaulipas, Michoacán, Guerrero, and Nuevo León, citing risks of further violence.

The killing comes amid U.S. pressure on President Claudia Sheinbaum's government to intensify anti-cartel efforts, including threats of direct intervention from the Trump administration. Many of Oseguera's relatives, including his son 'El Menchito' and wife Rosalinda González Valencia, have been arrested on U.S. and Mexican charges.

Experts anticipate power struggles within the CJNG, potentially leading to more bloodshed as factions vie for control.