The Zetas split from the Gulf cartel and by 2008 had operations in 28 major Mexican cities, according to an analysis by Grupo Savant, a Washington-based security think tank.
In February 2008, Lazcano sent Trevino Morales to Guatemala, where he was responsible for eliminating local competitors and establish Zetas control of smuggling routes. Trevino Morales was then named by Lazcano as national commander of the Zetas across Mexico despite his lack of military background, earning him the resentment of some of the original ex-military members of the Zetas, the official said.
The promotion involved Trevino Morales in virtually every decision by the Zetas, the official said.
Trevino rose to the top of the Zetas last year after leader Lazcano died in a shootout with Mexican marines in Coahuila state.
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.