Nemesio “El Mencho” Oseguera Cervantes was a feared drug lord and leader of the Jalisco New Generation Cartel (CJNG), one of Mexico’s most violent criminal organizations.

He had long been one of the country’s most wanted fugitives, and the United States had offered a $15 million reward for information leading to his arrest.

Oseguera was born in Michoacán in July 1966, then immigrated to the United States and was convicted in California in 1994 of conspiracy to distribute heroin.

After serving three years in prison, he returned to Mexico and worked as a police officer in the state of Jalisco, but soon resumed his criminal activities.

According to the U.S. Treasury Department, El Mencho has been deeply involved in drug trafficking since the 1990s.

He founded CJNG with his brother-in-law Abigael González Valencia, leader of Los Quinis, a family-based cartel operating in Michoacán state. The U.S. Drug Enforcement Administration said Ross Quinis served as CJNG’s finance and logistics unit and oversaw its “diverse network of money laundering activities.”

Before forming CJNG, Oseguera served as the head of hit squads for the Milenio cartel and then for the Sinaloa cartel, where he oversaw security and violence operations.

According to the DEA, CJNG emerged from the remnants of the Milenio cartel in the 2010s.

Mr. Oseguera has been indicted multiple times in the United States, including conspiracy to manufacture and distribute methamphetamine, cocaine, and fentanyl with intent to import into the United States in 2022.

The DEA said CJNG is a “major supplier of illicit fentanyl” to the United States, “not only derives billions of dollars in profits from the production of illicit synthetic narcotics, but is also one of the major suppliers of cocaine to the U.S. market” and has a presence in more than 40 countries.