The investigation into De Leon began on January 2011 when U.S. Border Patrol agents at the Hidalgo-Reynosa International Bridge seized a shipment of 15 rifles that had been hidden inside the gas tank of a truck.
Agents with the U.S. Bureau of Alcohol Tobacco Firearms and Explosives traced the weapons to a Dallas man who had sold the weapons to De Leon at a gun show just days before. The two men then met several other times to exchange firearms.
The Dallas man was identified in court records only as MSH and in one transaction recruited various individuals to illegally purchase more than 100 rifle receivers which De Leon then took to two other men who manufactured the rifles which .
