This plays out time and again. A man is fired from his job because his supervisors have grave doubts about his character. The dismissed employee broods, amasses a large arsenal <(explain to me again why that is still legal?) and ends up committing a revenge massacre against people associated with his former employer.
All of which merely demonstrates that his former bosses, contrary to his assertions, actually had great instincts and were very well advised to take the step of getting rid of him. Sorry, Chris Dorner, I am not going to buy your story of being a victim.