Once while traveling in the night train, he got attacked and mocked by a gang of three drunkards after his bouts of laughter provoked them. In self-defense, Arthur shot three of them and ended up having killed for the first time.
Among all of these hubbubs, His mother is his only confidence; he believes his mother is the only constant source of inspiration for him, one who he can call his own in a world that has given him reasons to turn cold. The discovery of the contents of his mother’s letters to Thomas Wayne is a breaking point in his life. His anger and resentment get to another level when he discovers in the letter that his mother allegedly had an affair with Thomas during her span of working at his place and that he is Wayne’s bastard child. He decides to confront Wayne, first at his place and second at an Opera show he had attended.
On encountering Wayne at the public loo, he arraigns him of hiding his identity as his father. Wayne loses his temper and denies the fact, instead of tells him that his mother was mentally ill and delusional and that Arthur was actually adopted. Arthur desperately needed to be heard, to be provided with the warmth, the security he lacked in his childhood. He is visibly despondent, disappointed when he says to Wayne,
“I know it seems strange, I don’t mean to make you uncomfortable, I don’t know why everyone is so rude, I don’t know why you are; I don’t want anything from you. Maybe a little warmth, maybe a hug dad, maybe a bit of common decency.”
For once, you cannot imagine this same vulnerable person to have any murderous intent.
From this point in Arthur spirals at greater pace in the depth of his own dark past. He is aware of the fact that this world is not his place to be. He visits the Arkham hospital to find out details about his own past. This is the place where his mother was admitted to when she had a mental breakdown.
On learning how he was brutally abused by his mother and her boyfriend, he finds out that his pathological laughter was a result of the brain damage caused by a young Arthur being tied to the radiator.
From Arthur Fleck To Joker
You have to pause here, and take a few moments to discern the amount of pain the knowledge about his past might have caused to him. It would be wrong to say that Arthur wasn’t trying to contain his wounds but these series of revelation led him to completely break down. He takes a moment to tell us how he felt about his miserable, hopeless life, “I used to think my life was a tragedy, but now I realize, it’s a fucking comedy.” Before he goes on to kill his ailing mother, right on the hospital bed. Arthur Fleck by now has lost control and is stealthily materializing into ‘Joker’ (somehow Arthur Fleck identified himself as Joker, more so than he did as Arthur, maybe because of the joke he had made out of unfortunate life.)
Arthur knew he was living a lie. For the most part of his life, he had been ignored, abused, mistreated and rejected in various insensitive ways. To Arthur, no amounts of killings could ever justify the damage the society did to him.
Ever since the subway killings, his conscience died and some twisted purpose started making sense to him. Humanity, sensitivity was not the ways to deal with the harsh reality. Disturbingly enough, he gave in to killing people, to avenge every bit of wrong done to him.
Arthur unintentionally becomes the symbol of Gotham’s revolution, inspiring other desperate people in the city. He finally starts to be aware of the attention people were giving him and this started feeding his sense of meaning. “For my whole life, I didn’t know if I really existed. But I do, and people are starting to notice.”