Maya Simpson is a drug addict and the girlfriend of spree killer Johnny Feist, Feist committing the killings in jewelry stores to rob them and feed their habits. Maya wasn't deeply involved but privy to the amiss anomaly of Feist not being able to afford the jewelry he pawned for their drugs.
Maya was arrested and taken into custody for interrogation in the interest of catching Feist in the act, as well as proving his mother Dede McCann ordered the robberies and murders. McCann found out about Maya's arrest, and when she was released, McCann killed her with a drug overdose to silence her, then locked her in the chest of the trio's apartment where the drugs would be prepared.
Feist was shown pictures of Maya dead in the chest, which broke him. he was angry enough to sell out McCann's involvement, leading to both of them being arrested. (CI: "Diamond Dogs")