The killing of Jalisco New Generation Cartel leader Nemesio Oseguera Cervantes during an attempt to capture him in Jalisco state was the highest-profile blow against cartels since the recapture of former Sinaloa cartel boss Joaquín “El Chapo” Guzmán a decade ago.

Following Oseguera Cervantes’ death, gunmen unleashed violence across the country. Cars burned out by cartel members blocked roads in 20 Mexican states and left smoke billowing into the air. People locked themselves in their homes in Guadalajara, Mexico’s second-largest city and Jalisco’s capital, and school was canceled Monday in several states as security forces were placed on alert all over the country. Even Guatemala reinforced security on its border with Mexico.

The killing could give the government a leg up in its dealings with the U.S. Trump administration, which has been threatening tariffs or unilateral military action if Mexico does not show results in the fight against the cartels.

But the long-term effect on Mexico’s security landscape remains unclear.

Here’s what to know:

‘El Mencho’ was the leader of a fast-growing criminal group

Oseguera Cervantes, better known as “El Mencho,” was 59 years old and originally from the western state of Michoacan. His ties to organized crime went back at least three decades.

In 1994, he was tried for trafficking heroin in the U.S. and sent to prison for three years. Upon returning to Mexico, he quickly rose through Mexico’s drug trafficking underworld.

Around 2009, he founded the Jalisco New Generation Cartel, which became Mexico’s fastest-growing criminal organization, moving cocaine, methamphetamines, fentanyl and migrants to the United States, and using violence with the use of drones and improvised explosive devices.

The cartel earned a reputation for brazen attacks on Mexican security forces, including downing a military helicopter in Jalisco in 2015 and attempting a spectacular, but unsuccessful, assassination of Mexico City Police Chief Omar García Harfuch, who is now Mexico’s federal security secretary.

It recruited aggressively, experimenting with new ways to reach potential members online, and generated revenue through fuel theft, extortion and timeshare fraud, among other activities.

Oseguera Cervantes died in a battle with troops sent to capture him

Oseguera Cervantes was killed during an attempt to capture him, as his followers attempted to fight off Mexican troops.

Mexico’s Defense Department said in a statement that the army launched an operation in the southern part of Jalisco state to capture Oseguera Cervantes, involving the Mexican Air Force and special forces.

The cartel counterattacked, and in the ensuing confrontation, federal forces killed four members of the criminal group, and wounded three others, including its leader, who died later during transfer by air to Mexico City, according to the statement.

Three soldiers were injured and two people were detained in the action. Rocket launchers capable of shooting down aircraft and destroying armored vehicles were seized at the scene.

Mexico is keen to show Trump results in the fight against cartels

Oseguera Cervantes’ will help Mexico’s government show results to the U.S., which is pressuring its neighbor to pursue drug cartels more aggressively. Both countries said intelligence cooperation helped lead to Sunday’s operation.

Oseguera Cervantes was facing multiple indictments in the United States and the U.S. State Department had offered a $15 million reward for information leading to his arrest. The Trump administration designated his cartel and others foreign terrorist organizations a year ago.

U.S. Deputy Secretary of State Christopher Landau, who was U.S. ambassador to Mexico during the first Trump administration, applauded the operation via X, writing: “The good guys are stronger than the bad guys. Congratulations to the forces of law and order in the great Mexican nation.”

Mike Vigil, former chief of international operations for the DEA, said Mexico had sent a “a strong message to Donald Trump’s administration that they are fighting aggressively and effectively” against the most powerful cartels. He added that “the majority of the information came from the Mexican armed forces and all credit goes to Mexico.”

Cartel leader’s death leaves a power vacuum

It’s not clear who will succeed Oseguera Cervantes, or if any one person can.

The Jalisco cartel has a presence in at least 21 of Mexico’s 32 states and is active in almost all of the United States, according to the U.S. Drug Enforcement Administration. But it is also a global organization and the loss of its leader could be felt well beyond Mexico.

“El Mencho controlled everything, he was like a country’s dictator,” Vigil said.

His absence could slow the cartel’s rapid growth and expansion and leave it initially weakened against the Sinaloa cartel on several fronts where they or their proxies are fighting. The Sinaloa is locked in its own internal power struggle, however, between the sons of “El Chapo” and the faction loyal to Ismael “El Mayo” Zambada, who is in U.S. custody.

Vigil said Mexico should seize the moment to launch “an effective frontal assault based on intelligence.”

“This is a big opportunity for Mexico and the United States if they work together,” he said.

Security analyst David Saucedo said that if relatives of Oseguera Cervantes take control of the cartel, the violence seen Sunday could continue. If others take power, they could be more willing to turn the page and continue operations.

The greatest fear would be that the cartel turns to indiscriminate violence. They could decide to “launch narcoterrorism attacks … and generate a scenario similar to what Colombia lived in the 1990s,” a full-on attack against the government “car bombs, assassinations and attacks on aircraft.”