The attorney general in the violence-torn border state of Coahuila says the fatal shooting of the governor's nephew came hours after one of Mexico's most-feared drug bosses was killed by state police.

Attorney General Homero Ramos says revenge "could be a hypothesis" for the slaying of 25-year-old Jose Eduardo Moreira, whose body was discovered on Wednesday. Ramos' office says seven local police officers have been interrogated in connection with slaying in the city of Acuna, across the border from Del Rio, Texas.

Ramos told Radio Formula on Friday that hours before Moreira was killed, a confrontation between state officers and suspected cartel members left five suspects dead, including the nephew of Zetas cartel leader Heriberto Lazcano Lazcano.