This story is developing and will be updated as we learn more.

Nemesio “El Mencho” Rubén Oseguera Cervantes, founder and top leader of the Jalisco New Generation Cartel (CJNG), was killed by federal forces Sunday morning, according to the Ministry of Defense.

The operation was led by the Army and federal forces in Jalisco in an area known to be controlled by El Mencho.

In a press release, the Ministry of Defense said that during an operation to arrest El Mencho, Mexican military forces came under fire and were forced to defend themselves. Four CJNG operatives were killed in the firefight. Three more, including El Mencho, were gravely injured. They were air lifted to Mexico City but died en route, the Defense Ministry said.

In addition to Mexican military intelligence, United States authorities contributed information used to carry out the operation, the ministry said.

Reports of security operations started circulating this morning in the municipality of Tapalpa, a town located some 90 kilometers south of Guadalajara, the state’s capital. Residents in that area reported overflights and the presence of military convoys, which foreshadowed a large-scale deployment.

Later, road blockades were reported in at least six states: Jalisco, Michoacán, Colima, Tamaulipas, Guanajuato and Aguascalientes.

Videos that circulated on social media showed the burning of vehicles and public buses in Puerto Vallarta, Guadalajara and Tapalpa. Residents also reported burnings of pharmacies and convenience stores in different parts of Guanajuato.

In Puerto Vallarta, residents reported that the city was under siege by men on motorcycles and the sound of gunshots.

Authorities are maintaining active operations in several states to contain possible reactions and reinforce security following one of the most significant events in the fight against drug trafficking in recent years.

Who was ‘El Mencho’?

“El Mencho” was considered the top leader of the CJNG, one of the most powerful and violent cartels in Mexico, with a strong presence in Jalisco, Colima, Michoacán and other states. He also played a key role in the trafficking of methamphetamine and fentanyl to the United States.

The U.S. Department of Justice had issued federal charges against him and offered multimillion-dollar rewards for information leading to his capture.

El Mencho’s death opens the door to possible internal reshuffling, succession disputes and risks of increased violence in territories where the CJNG operates, something that security specialists see as a likely scenario after the fall of such a concentrated leadership.

With reports from Milenio, El Informador, Se Uno Noticias, and El Financiero