Psychopath Diary - It's been a while since I watched this one. A very mild and miserable office worker is about to commit suicide (at a construction site?) when he witnesses the murder of a homeless man. While escaping he (1) hits his head and (2) finds the killer's dropped diary. He believes that the diary is his, which gives him all sorts of self-confidence. And of course the real psycho wants his diary back.
