He Was a Quiet Man (2007) on Netflix

In Los Angeles, the lonely and paranoid Bob Maconel is a complete loser: at home, in spite of living in the same address for five years, his next door neighbor ignores his existence and he only talks to his alter-ego golden fish in his aquarium; in the office at ADD company, he is abused and humiliated by his colleagues and nobody has ever asked an opinion to him or invited him to a happy-hour. Every now and then Bob imagines shooting five loath coworkers or blowing up ADD's building. When his next cubicle colleague has a breakdown and shoots his colleagues, Bob kills him with five shots and becomes a popular local hero. His boss Gene Shelby moves him from his cubicle to an office in the last floor and makes him the VP of Creative Thinking as the substitute for Vanessa Parks, who has become quadriplegic with one bullet in her spine. Bob visits Vanessa in the hospital and after the initial rejection, she asks him to help her to commit suicide. However, they become close and Bob falls in love for Vanessa. But the mistreatment in the past and lack of confidence of the quiet Bob haunt him, driving him to an insanity process.