The man who would be known as the Joker was born in Gotham City as Arthur Fleck, supposedly the adoptive-son of Penny Fleck while it’s unknown who his alleged true parents are. As the film's script specified, Arthur was in his 30's during the film's events which took place in 1981 meaning he was born between 1942 and 1951. When he was raised by his adoptive-mother and her boyfriend they abused him as Penny was obsessed with Thomas Wayne would neglect him and allow her boyfriend to physically and emotionally abuse him, which further contributed to his mental health and pathological laughter. This eventually caused him to develop a condition called the Pseudobulbar affect; a psychological disorder that causes him to release uncontrollable laughter in unsuitable moments. This most often occurs after trauma such as after being curb-stomped at the start of the film or after killing his mother. Ever since he was young, Arthur sought to become a popular comedian so he could bring laughter and joy which his mother raised him to believe in and even kept his true family lines as secrets. Following his firing, Authur goes on the subway home still in his costume but is watching as a young woman being harassed by three young and wealthy Wall Street stockbrokers from Wayne Enterprises. Seeking to save her, he bursts out in uncontrollable laughter which draws the trio's attention so the woman is saved, but Arthur is beaten and bullied violently by them until he pulls out his gun which was loaned for him by his associate so he can protect himself. During the massive clown riots, one of the protesters kills Thomas and Martha Wayne and takes Martha's pearl necklace much to Bruce's horror. This makes the Joker indirectly responsible for the death of the Waynes and the rise of Batman.