Most likely a very organized group of guys pulled it off, and probably a lot of planning and mapping of the stores' strength and weakness were put in.
These kind of heist can be planned within months but coming up with the guts to do it is even harder. Anyway these guys would be smart to sell these guns slowly and not all at once or even repaint them or change about to use for their own use.
But although they may be organized, they most likely left some evidence behind unless they watched a lot of CSI. A crime like this can be solved if the thiefs do something retarded and return to the scene of the crime, sell the guns in some mass sale on ebay, or gloat about it when they are on the field.
But if they do get away with it, sooner or later they may take real guns and then hit up banks, but robbing a US bank won't be a walk in the park as robbing a Canadian bank
- Pistolero Steve