I originally mentioned garrisons because that was the case with ISIS, Boko Haram and Libya but way back in Hussein's Iraq and Taliban Afghanistan there were weapon and ammo caches hidden everywhere.
So it our case it would be NG garrisons, sheriff's HQ's, police stations, mosques, community centers, clubs of this or that, schools, mansions of activist judges (see Sendero Luminoso in Peru), any guncontrol VIPs, etc.
I do think there are either hidden weapon stockpiles or government ones set up for easy pickings or both. This is why we must stay vigilant.