Oliva Castillo, Zetas Cartel.

The three northeastern states that Oliva Castillo allegedly oversaw are some of the Zetas' strongest-held territory. Authorities say that much of the violence registered in these states is the result of the Zetas fighting rival groups such as the Gulf cartel and Sinaloa cartel, for access to lucrative smuggling routes.

But the Zetas -- especially in their strongholds -- have branched out from drug trafficking and into extortion of businesses, kidnappings, and human smuggling.

The deadly attack that Oliva Castillo is accused of ordering is the casino arson in the city of Monterrey where 52 people died. Officials allege that the attack happened because the casino owners did not comply with payments to the cartel.

More is here.