MEXICO CITY — The Mexican army killed the leader of the Jalisco New Generation Cartel, Nemesio Ruben Oseguera Cervantes, “El Mencho,” on Sunday, decapitating what had become Mexico’s most powerful drug cartel and thrusting swaths of the nation into chaos.

The drug lord was the Mexican government’s biggest prize yet to show the Trump administration in its efforts to crack down on the cartels, and his death was met with a forceful reaction from the cartel, known by its Spanish initials CJNG.

Cars burned out by cartel members blocked roads in nearly a dozen Mexican states and left smoke billowing into the air. Jalisco’s capital, Guadalajara, was turned into a ghost town Sunday night as civilians hunkered down. School was canceled Monday in several states.

Oseguera Cervantes was wounded in an operation to capture him Sunday in Tapalpa, Jalisco, about a two-hour drive southwest of Guadalajara and he died while being flown to Mexico City, the Defense Department said in a statement. The state is the base of the cartel known for trafficking huge quantities of fentanyl and other drugs to the United States.

During the operation, troops came under fire and killed four people at the location. Three more people, including Oseguera Cervantes, were wounded and later died, the statement said. Two others were arrested and armored vehicles, rocket launchers and other arms were seized. Three members of the armed forces were wounded and receiving medical treatment.

White House Press Secretary Karoline Leavitt said via X that the U.S. government provided intelligence support for the operation. “‘El Mencho’ was a top target for the Mexican and United States government as one of the top traffickers of fentanyl into our homeland,” she wrote. She commended Mexico’s military for its work.