Has anyone said WHY??? - this was allowed to be done?
The unasked question:
Was Gun Runner a plan to secretly plant hundreds of US guns at the scenes of Mexican crimes, in order to politically justify infringements on the firearms rights of US citizens?
Well, in a word: YES
More to the point, the plan was for the Mexicans to submit firearms serial numbers of weapons they seized to the ATF for verification that they came from the US and thereby provide justification to further restrict access to firearms in the US.
The guns were not to be "planted" but rather to be used by the drug gangs and either picked up at the scenes of drug violence (wherein a dead/wounded drug gang member dropped the weapon) or in seized in raids of drug gang cache's.