Rampage (2009) on Netflix

Plot summary

In Tenderville, Oregon, twenty-three-year-old Bill Williamson lives with his parents and works a low-paid job as a mechanic. He feels surrounded by the world's troubles, by televisions and radios everywhere, and by the political opinions of Evan Drince, who appears to be his only friend. His parents want him to move out. On his way to work he buys coffee, then argues with the shop owner about it, and at the garage his boss interrupts him while he works on a personal vehicle off the clock and refuses him a raise. Bill prints counterfeit money and assembles steel armor for his body, along with a bullet-resistant helmet and a paintball mask, then arms himself with two submachine guns, two pistols and two knives.