Large scale gun thefts are sometimes trafficked to Mexico, or other black market hot spots. But how did the bandits know where the guns were, how did they get access with a U-Haul truck?
Smacks of inside coordination.
Four hundred guns is a lot, but not exactly enough to equip an army. To hear law enforcement in borderline panic mode makes law enforcement seem cowardly and inept.
If there's credible information of an insurrection planned in connection with the theft, that might be different.
Update: Guns recovered. They were apparently on their way to Chicago.