Ian Chase

Ian Chase was a socialite and presumed mobster, as well as a murderer.

Batman: Arkham Origins Incident
Chase was a wealthy socialite and mobster affiliated with Black Mask's Gang (Which was then taken over by Joker). At some point Chase was in a serious relationship with Clarissa Rodriguez, but she left him for his best friend, the more wealthy Horace Riley. During a Halloween Party at Wayne Manor, Ian Chase ended up causing a disturbance (presumably by harassing Clarissa, based on a comment made by Alfred), which forced Bruce Wayne to throw him out.

Two months later, on Christmas Eve, Chase went to Crime Alley and proceeded to murder both Clarissa and her now fiancée Horace by shooting him in the lung and shooting her in the heart, respectively, coincidentally at the same spot that Bruce's parents had been murdered (it's implied that he did that out of a grudge from a unrequited love triangle, where Clarissa went with Horace instead of him).

Although Chase managed to clean up the area by removing most of the bullet casings, he missed one inside of the grate. Batman, Bruce Wayne's alter ego, managed to uncover the murder and deduced Chase's role in their murder. Batman then tracked Chase down to the Industrial District, near the Sionis Steel Mill where Chase alongside other mobsters, were discussing his role in the murder (the dialogue suggested that he would have been the number one suspect in Riley and Rodriguez's murders, but could not be convicted without proof).

Batman then ended up attacking Chase and nearly killing him due to his petty reason for committing the murders and partially due to the location of the shooting reminding him of the murder of his parents before Alfred calmed him down. He then knocked Chase out and left him to be arrested by the GCPD.