There's 120 guns per 100 people in the US, a huge veteran population with combat training, most of them armed, multiple armed paramilitaries, militia groups, and a large number of people with military-grade munitions and equipment all over the nation. As the old quote goes, "behind every blade of grass, a gun". It only takes about 3.5%. And there's only a few million people in the government, and 300 million disgruntled individuals, many of whom know the exact tactics, exact procedures, cryptographic codes, techniques and practices of infantry, marines, special forces, SWAT, police, the DHS and ICE. Not to mention, disgruntled active-duty servicemembers on the inside - the "insider threat" they keep lecturing us about.