More than two decades before Nemesio Rubén Oseguera Cervantes built the violent cartel that made him one of the most wanted fugitives in Mexico, he was a young man selling drugs on the streets of San Francisco.
The killing of 59-year-old Oseguera Cervantes by the Mexican army on Sunday brought renewed attention to the powerful drug lord known as “El Mencho,” including his early beginnings as a small-time drug dealer in the Bay Area, where he lived with family.
The Mexican-born Oseguera Cervantes crossed at least three times into the U.S., where he ended up jailed in San Francisco on two occasions in the late ’80s and later served prison time in California for a heroin trafficking case, according to court records and media reports.
The San Francisco Police Department declined to provide information about the arrests.
In 1986, Oseguera Cervantes was first arrested at age 19 in San Francisco, where cops caught him trying to sell a small stash of drugs, according to a Courier Journal investigation. Mugshots published by the Courier Journal show Oseguera Cervantes wearing a blue hoodie and gazing into the camera with a slight frown as police booked him into jail.
After being deported to Mexico, Oseguera Cervantes returned to San Francisco, where he was jailed in 1989, the investigation found. By then, his face had filled out as a 22-year-old and he wore a denim jacket in his booking photo.
In 1992, according to the Courier Journal report, he and his brother sold heroin for $9,500 to two undercover officers at the Imperial Bar in San Francisco.
The case landed both brothers in federal court. They eventually pleaded guilty and accepted a plea deal, court records show. Abraham Oseguera-Cervantes, who had a prior felony and was found with a firearm in the drug bust, was sentenced to 10 years in prison in 1993; Ruben Oseguera-Cervantes was sentenced to five years the following year.
Court records indicate he was held at Santa Rita jail while the case was pending, and was ordered moved to the federal prison in Pleasanton, which has since closed.
Even at the time, according to court records, he went by the nickname that would define his reign as a drug lord: Mencho.
Back in Mexico, Oseguera-Cervantes formed the Jalisco New Generation Cartel in 2009, according to the State Department. It grew into one of the most violent drug cartels in Mexico, with the highest cocaine, heroin and methamphetamine trafficking capacity in the country, U.S. officials said.
In recent years, officials said, the cartel has been responsible for trafficking fentanyl into the U.S., where the deadly drug has devastated cities like San Francisco. More than 600 people have died from accidental drug overdoses in San Francisco in each year since 2020, with the majority of those deaths fentanyl-related.
National Guards patrol the area outside of the General Prosecutor’s headquarters in Mexico City on Feb. 22, 2026, after authorities reported that the Mexican Army killed Jalisco New Generation Cartel leader Nemesio Oseguera Cervantes. (Ginette Riquelme/Associated Press)
In December 2024, the U.S. State Department offered a $15 million reward for information leading to the arrest or conviction of Oseguera Cervantes, who by then was one of the most wanted fugitives in Mexico.
The cartel has been responsible for “many homicides” against rival trafficking groups and Mexican law enforcement officers, according to the State Department.
The operation in which Oseguera Cervantes was killed was carried out by Mexican special forces “with U.S. authorities providing complementary intelligence,” the U.S. Embassy in Mexico said Sunday.
His death unleashed a wave of violence over the weekend by members of his Jalisco New Generation Cartel, who blocked roads with burning vehicles in a retaliatory display across Mexico.
Many U.S. and Canadian airlines canceled flights to and from Puerto Vallarta and Guadalajara, leaving tourists stranded. The U.S. government issued a security alert warning U.S. citizens in those cities and other parts of Mexico to shelter in place.
This article originally published at Cartel leader ‘El Mencho’ was first caught dealing drugs in San Francisco at age 19.