"Half of what we seize, 55 percent are assault rifles. And this is what gives these groups this intimidation power. Over 17,000 assault rifles, throughout the last two years. Two thousand and 200 grenades, missile and rocket launchers. Fifty caliber sniper rifles," the attorney general explained.
It might surprise you to learn where all these guns are coming from. It turns out 90 percent of them are purchased in the US.
"The Second Amendment was never designed to arm criminal groups, and especially not foreign criminal groups as it is today," Medina-Mora said.
Asked if he blames the U.S. for not doing more to stop this flow, he told Cooper, "We believe that much more needs to be done. We need a much more committed effort from the U.S."
"There was an assault weapons ban in the United States for ten years. It expired in 2004. Would you consider asking Congress to reinstate that?" Cooper asked Napolitano.
"I haven't thought that far," she replied. "What I have worked on is working with customs, with ATF and saying "what do we need to do by way of identifying who is putting these unlawful gun into the hands of the traffickers who are using them to murder people. And what do we need to do to stop it."
It isn't just guns coming from the U.S. that's fueling Mexico's war: it's cash. According to estimates, drug trafficking brings in as much as $38 billion a year from the U.S.
"How much responsibility does the United States have in helping Mexico in ending this war?" Copper asked Medina-Mora.
"This is a shared responsibility," the attorney general replied.
"'Cause there's many in the U.S. who see this as a Mexican problem," Cooper pointed out.
"If demand comes from the U.S., if cash coming from people acquiring and consuming drugs in the U.S., if weapons are coming from the U.S. this is a shared responsibility," Medina-Mora argued.
To find out how cartels are smuggling cash and drugs so easily across the border, 60 Minutes decided to visit one of Mexico's most famous alleged traffickers - Sandra Avila Beltran. She's the subject of a bestselling book and there's even a song about her.