Miguel Angel Trevino Morales, the notoriously brutal leader of the feared Zetas drug cartel, has been captured in the first major blow against an organized crime leader by a Mexican administration struggling to drive down persistently high levels of violence, a U.S. federal official said Monday.

Several Mexican media outlets reported that Trevino Morales was captured by Mexican Marines in the border city of Nuevo Laredo, which has long served as the Zetas’ base of operations. The U.S. federal official was not authorized to speak to the press and asked not to be identified.

Trevino Morales, known as “Z-40,” is uniformly described as one of the two most powerful cartel heads in Mexico, the leader of a corps of special forces defectors who splintered off into their own cartel in 2010 and metastasized across Mexico, expanding from drug dealing into extortion, kidnapping and human trafficking.

Along the way, the Zetas authored some of the worst atrocities of Mexico’s drug war, leaving hundreds of bodies beheaded on roadsides or hanging from bridges, earning a reputation as perhaps the most terrifying of the country’s numerous ruthless cartels.

The capture is a public-relations victory for President Enrique Pena Nieto, who came into office promising to drive down levels of homicide, extortion and kidnapping but has struggled to make a credible dent in crime figures. It adds to the long list of Zetas’ leaders who have been captured or killed in recent years, including Zeta head Heriberto Lazcano Lazcano, who was shot to death last year.

The debilitation of the Zetas has been widely seen as strengthening the country’s most-wanted man, Sinaloa cartel head Joaquin “El Chapo” Guzman, who has overseen a vicious turf war with the Zetas from hideouts believed to lie in rugged western Mexico.

Trevino Morales, who is in his early 40s, is expected to be succeeded by his brother, Omar, a former low-ranking turf boss seen as far weaker than his older brother.

Miguel Angel Trevino Morales began his career as a teenage gofer for the Los Tejas gang, which controlled most crime in his hometown across the border from Laredo, Texas. He soon graduated from washing cars and running errands to running drugs across the border, and was recruited into the Matamoros-based Gulf cartel, which absorbed Los Tejas when it took over drug dealing in the valuable border territory.

Trevino Morales joined the Zetas, a group of Mexican special forces deserters who defected to work as hit men and bodyguards for the Gulf cartel in the late 1990s.

Stories about the brutality of “El Cuarenta,” or “40” as Trevino Morales became known, quickly become well-known among his men, his rivals and Nuevo Laredo citizens terrified of incurring his anger.

“If you get called to a meeting with him, you’re not going to come out of that meeting,” said a U.S. law-enforcement official in Mexico City, who spoke on condition of anonymity because of the sensitivity of the topic.

One technique favored by Trevino Morales was the “guiso,” or stew, in which enemies would be placed in 55-gallon drums and burned alive, the official said. Others who crossed the commander would be beaten with wooden planks, he said.

Trevino Morales was indicted on drug trafficking and weapons charges in New York in 2009 and Washington in 2010, and the U.S. government issued a $5 million reward for information leading to his arrest.

According to the indictments, Trevino Morales coordinated the shipment of hundreds of pounds of cocaine and marijuana each week from Mexico into the U.S., much of which had passed through Guatemala.

He also moved bulk shipments of dollar bills back into Mexico, the documents say.

Trevino Morales’ brother, sister and mother lived in Dallas but he had many relatives around Nuevo Laredo and, while moving frequently to avoid authorities, he was believed to often return to his hometown, the U.S. official said.