Unintended Consequences
Government oppression of gun owners sends the protagonist over the edge when, thinking he is stopping a robbery, he foils a BATF raid on a friend's house. Our hero then plans a sequence of targeted assassinations of antigun politicians and government agents. As he (and various independent operators who emulate him) start making it very hard to be a jackbooted thug, a dedicated FBI agent (the main antagonist) races to discover the protagonist's identity...