The strategy known as "gun-walking", allowing suspected straw purchasers to leave gunstores with weapons with the intent of tracking them, was barred under a long-standing departmental policy.
That information wasn't forwarded to the federal database maintained by the Federal Bureau of Investigation used by gunstores in conducting background checks, and should have stopped him from buying a gun.
Ninety per cent of the guns used in the current wave of drugs violence came from the US, he said, and he pointed out that there were 11, 000 gunstores in towns and cities close to the Mexican border.
In 2008, it partnered with Mayors Against Illegal Guns to create a video database of gun purchases at its stores and said it would trace any firearms bought from its stores that were later used in a crime.