A Mexican official says that the 12 agents under arrest for shooting at a U.S. Embassy vehicle and wounding two U.S. employees inside were investigating a kidnapping.

Federal Police regional security chief Luis Cardenas Palomino says the kidnapping occurred hours before the agents fired at the SUV that was carrying the two Americans and a Mexican navy captain.

The Mexican navy said the three were headed to a navy training site in a rural area south of Mexico City.

Palomino made the comments Sunday after announcing the detention of David Rosales, whom he said was leader of the Gulf drug cartel in the northern state of Nuevo Leon.

Palomino said Rosales is known as "Commander Devil" and coordinated attacks on bars in the city of Monterrey that killed several people.