Concerned citizen reports a pistol purchase and provides a plethora of details, but won't identify himself? Mr. Anon is either (1) a scumbag who would never bother to report this in the first place or (2) a good guy like a NFOA member who would gladly identify himself and be willing to testify or (3) someone with a grudge against this family. Nice to know all it takes for #3 to launch a 10-month Fed investigation is to make a pay-phone call from, say, the back lobby of the Cornhusker Hotel.
So then they bring in an ex-scumbag to score a 10/22! That will show the seller he's dealing with a well-intentioned buyer... after all, what would a criminal, sociopath or terrorist do with "that little thing?" They follow-up with a defensive shotgun purchase just to continue to make the buyer seem harmless as far as a threat to society. Then they are rebuffed at the AK purchase and bring in the "legitimate" associate to complete the transaction. Then toss in the purchase of the ammo (.223) before the gun (AR15) to add to the months of confusion (see bullit above) and finish with the wicked AK with Folding Stock piece de resistance!
I don't know the Gerbig family, but I sure have a dislike for "stings" in general... doubt I'll end up on this jury.