Damn narcos, They just keep getting more sophisticated.
Not really that hard. They have their cousin or home boy who has US citizenship go into a gun store and buy anything they want. Then they report them all stolen as to take the heat off themselves. Cars are checked less going down into Mexico, compared to coming into the US, so its easy to smuggle a trunk load of them to the cartels. Or the black market, aka, criminals selling stolen guns. Its easy to use our laws and rights against us. Crooked US gundealers who let illegals and criminals knowingly buy and a few LEO's play a role into it as well.
The beat and well used AK's on that table look like they came from south of Mexico.
Those are some nice systems. Yet why does every bad guy have to go and ruin a nice 1911 or AK esp. the fist one you posted man is that hideous. Along with the gold plated AR's and Silver Plated ones also.