Buried deep in this long article about Tex-Mex drug running is info about who has trained the cartel members....
http://www.dallasnews.com/sharedcontent/dws/news/localnews/stories/061905dnmetmimicourt.222e0d0b.htmlInformants told U.S. drug investigators that they suspected that a criminal organization – built around an elite band of former Mexican military commandos working for the Gulf cartel – was responsible for the attack on Mr. Lugo.
The Zetas, as they are known, originally were trained in the U.S. by Army special forces to battle drug lords back in Mexico. But a small group broke away from the Mexican military in 2001 for more lucrative jobs as Gulf cartel enforcers. "Dallas is the new Miami for transiting drugs," said Mr. Jordan, former head of the DEA's El Paso Intelligence Center, which studies the drug trade. "Drug traffickers kill for I-35."
The Gulf cartel has a support system of about 500 members, among them the Zetas and their acolytes, who are the enforcers for the organization. Its tentacles reach well into the United States, and Dallas is considered a top transit point.
The Zetas have also carved a niche in the business of human smuggling, charging a 10 percent commission for use of the border and the Interstate 35 corridor.