3)You are currently an officer with Customs and Border Protection, tasked with the inspection of vehicles entering the United States through the U.S - Mexican border. On a regular day, you may confiscate a few small weapons, but on this day, you inspect a large recreational vehicle, which is found to contain a multitude of high-capacity firearms, as well as improvised explosive devices - similar to those in use in Iraq and Afghanistan. There is only one driver of the RV, a Mexican citizen, who appears genuinely surprised at the discovery of the weapons cache. You suspect that he may simply be a hired hand to unknowingly move illegal weapons into the United States.

1)What do you do at this point?

2)How many agencies do you think will ultimately be involved with discovering the intended target for these weapons?  Which agencies, and why would they be incolved?

As a Customs and Border Protection officer charged with inspecting vehicles entering the United States via the U.S.-Mexican border and finding such an incident as a responsible authority, I will take all these materials into custody immediately and notify ATF (Bureau of Alcohol, Tobacco, firearms and Explosives) about such.
After that, the Immigration and Customs Enforcement Department of Homeland Security will be provided with such information.
In such a case, if the driver is unknowingly involved in such an incident, then according to service ethics. I will take him into custody for further investigation and will contact the Mexican Authorities concerned to verify the identity and intent of the owner of such a company and will take the requisite inter-border cooperation measures and ensure that he can get justice if Driver is innocent.
As mentioned above, the name of the agencies for further actions would be involved in such incidents. They will be interested because they have been assigned the mission of preventing illicit smuggling of such products through borders and another department dealing with prohibiting and controlling such trade by migrants or immigrants attempting to do so illegally.