The alleged kingpin of an international drug-trafficking operation, Jose Maria Guizar Valencia, is in custody in Mexico after being arrested in the capital Thursday, authorities say.
The Zetas cartel leader, also known as Z43, was ambushed by national marines and federal police in Roma, one of Mexico City's more affluent neighborhoods.
Among the top 122 on Mexico's most-wanted list, he operated one of the most violent drug cartels in the region, stretching from the United States to Mexico and other parts of South and Central America.
"Los Zetas, under the command of Guizar Valencia, have murdered an untold number of Guatemalan civilians during the systematic overtake of the Guatemalan border region with Mexico during recent years," the bureau said.
Valencia reportedly holds dual citizenship with Mexico and the United States and a US$5 million dollar reward for his arrest was filed in 2014 with the U.S. State Department.
He is accused of being responsible for the annual export of "thousands of kilograms of cocaine and methamphetamine" to the United States, according to the State Department. An extradition request is expected.
"He was one of the top underbosses of the Zetas: this guy steadily rose up the ranks, and he actually started as a hitman for the Zetas," said Mike Vigil, former international operations chief for the U.S. Drug Enforcement Administration.
"This is a very good hit," Vigil said of the arrest. "It's a good feather in the hat of Mexican justice."
Government minister Alfonso Navarrete applauded the military for their coordination and investigation strategies leading up to the arrest.
The Zeta cartel is said to be one of Mexico's most cruel organizations. It has been implicated in numerous human-rights violations, including the massacre of 72 migrants in the summer of 2010; starting a fatal fire in 2011 at Monterrey Casino, which killed 52, and melting enemies in barrels of "stew."