Two of the guns were reportedly used in the murder of a Border Patrol agent in December.
After a few years of economic decline, mayors throughout Baja California, Mexico, have launched a campaign to convince Americans that their cities are safe, and open to foreign investment.
The Army said the six men and three women were working for the Zeta cartel. They said the gunmen mistook the agent's SUV for a rival drug gang.
"The ICE agents said we're Americans, we're diplomats. And the response from the Zetas was to open fire on the agents."
Hundreds of Border Patrol agents filled part of the baseball stadium in a sea of olive green. A line of riflemen stood at attention as the American flag and the agency's own flag fluttered in the cool morning air.
By late this week, nearly a million Mexican citizens will drive south on America's highways, headed home for the holidays. The Mexican government will be at the border waiting for them with open arms and beefed-up security. For good reason: the travelers come flush with cash and gifts.
The diplomatic missives released by Wikileaks last week show that the U.S. was quietly dismayed by Mexico's inability to dismantle its powerful cartels. But they also give deeper insight into the role that U.S. intelligence has played in Mexico - and some concern that rival political parties can change that.
Even as the U.S. government publicly celebrated Mexico's operations against the cartels, State Department officials quietly expressed concern over its failings. Government cables released by Wikileaks this week show a drug war in tatters.
The U.S. State Department has ordered its consular employees to use only armored cars when driving in the Mexican state of Sonora.
Citing concerns of violence in Mexico, the state of Arizona has ordered its fruit and vegetable inspectors not to cross the border to check the goods coming into the state. The produce industry says the mandate leaves them unprepared to deal with the resulting backup.