(The Lion) — Mexican security forces killed cartel boss “El Mencho” in an operation that U.S. officials say was aided by American intelligence support, delivering a blow to the fentanyl trafficking network.

The development takes place after Mexican President Claudia Sheinbaum has argued for months she doesn’t have the legal authority to go after narcoterrorists.

Nemesio Oseguera Cervantes, the 59-year-old leader of the Jalisco New Generation Cartel (CJNG) was one of the most wanted drug kingpins in the hemisphere.

He was fatally wounded in Sunday’s raid and later died en route to medical care, Mexico’s Defense Ministry said, according to the Washington Examiner.

CJNG has grown over the past 15 years into an extremely violent cartel responsible for huge quantities of fentanyl, methamphetamine, cocaine and other hard drugs funneled into the United States, said the Examiner.

The U.S. had offered a reward of up to $15 million for information leading to the kingpin’s arrest, and the Trump administration designated the cartel a foreign terrorist organization.

White House press secretary Karoline Leavitt said the United States provided “intelligence support to the Mexican government” in the recent operation.

Along with El Mencho, three other cartel members were killed and two others were arrested, underscoring heightened cooperation between U.S. and Mexican security forces said Leavitt, reported the Washington Times.

Leavitt emphasized that eliminating El Mencho was a priority for the Trump administration, which has aggressively pushed Mexico to intensify its crackdowns on transnational cartels that export lethal drugs northward.

“President Trump has been very clear – the United States will ensure narcoterrorists sending deadly drugs to our homeland are forced to face the wrath of justice they have long deserved,” she said.

U.S. Deputy Secretary of State Christopher Landau said on social media that the El Mencho operation was “a great development for Mexico, the U.S., Latin America, and the world,” while warning that cartel retaliation might fuel further violence.

“I’m watching the scenes of violence from Mexico with great sadness and concern,” he added. “It’s not surprising that the bad guys are responding with terror. But we must never lose our nerve.”

The operation sparked immediate unrest across several Mexican states, with CJNG affiliates burning vehicles, setting up roadblocks and clashing with security forces in a wave of retaliation after news of El Mencho’s death, reported Fox News.

Mexican authorities said multiple highways were blocked and intense security operations were underway to restore order.

Gunfire was reported in Guadalajara, as CJNG operatives were seen setting gas stations on fire, according to Axios.

Officials reported that Mexican forces seized weapons, armored vehicles and materials capable of downing aircraft during the operation.

Mexico Security Secretary Omar García Harfuch said 25 members of the National Guard were killed in Jalisco in six separate attacks after the death of Oseguera, reported the Associated Press.

The U.S. Embassy in Mexico urged American citizens to “shelter in place” in affected areas as violence erupted. Several flights were canceled at major airports near the violence, including those serving the popular resort destination of Puerto Vallarta.

“Due to ongoing security operations and related road blockages and criminal activity, U.S. citizens in the named locations should shelter in place until further notice,” the U.S. Embassy & Consulates in Mexico said.

Sheinbaum acknowledged the tense situation but tried to reassure the public.

There is absolute coordination with the governments of all states; we must remain informed and calm,” she said on X. “The social media accounts of the Security Cabinet provide permanent updates. In the vast majority of the national territory, activities are proceeding with complete normality.”

Still, it marks a radical departure from her previous rhetoric, claiming she had no authority to go after the narcotics trade with military force.

“Returning to the war against the narco is not an option. First, because it is outside the framework of the law,” she said at a press conference recently, a comment that’s not been widely reported in English-language media.

The Mexican president previously called targeted attacks on the cartel “a license to kill, it is a step towards fascism.”

President Trump has repeatedly signaled his administration’s intent to back tougher measures against drug cartels.

He has long criticized Mexico for not doing enough to confront cartel violence and has at times floated the idea of unilateral action to stem the flow of illicit drugs into the U.S.

El Mencho’s death marks one of the most significant developments in the decades-long battle against organized crime in Mexico. It could signal the country’s growing determination to stamp out narcotics traffic that fuels corruption inside Mexico.

“Ever since President (Claudia) Sheinbaum has been in power, the army has been way more confrontational, combative against criminal groups in Mexico,” David Mora, analyst for International Crisis Group in Mexico told the AP. “This is signaling to the U.S. that if we keep cooperating, sharing intelligence, Mexico can do it; we don’t need U.S. troops on Mexican soil.”