There's a reason they call it "Going Postal"
Digby chronicles the rise of the militarized police force in the US.
The only thing I have to add: After Vietnam, the occupation that was the easiest to enter and the best compensation right away for returning soldiers was the Postal Service. Vets who could do well on the civil service exam got extra points for each deployment, and lots of them became mailmen.
When their PTSD went untreated, many of them went bananas and started shooting up post offices across the nation. These mail carriers did not have access to combat weapons, most of which were banned for civilian use at the time.
These days, the combat vets are hiring on with police and the FBI and the private security forces across this nation. They are equipped with military style weapons and armament, they are used to controlling a civilian population that they either distrusted or despised or suspected of trying to kill them. They are used to having no compunction about damaging that civilian population. They are used to breaking down doors and shooting the first thing that moves.
What happens when they start "Going Postal"? Do we really want to unleash that upon our towns and neighborhoods?