Mexican drug runners powered by U.S. guns

As Mexico's drug violence spills into the U.S. and officials warn tourists of the danger, Mexican officials say more than 90 percent of all drug trafficking weapons are obtained from dealers and gun shows in the U.S. NBC News' Mark Potter reports.

VIDEO: Mexican drug runners powered by U.S. guns

Related links:
Mexican cartels' drugs, mayhem hit U.S. cities
Council on Foreign Relations analysis: Mexico's drug war looms large for U.S.
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