Spoiler warning: Plot and/or ending details follow.
In the aftermath of the massacre, Shannon met Starfleet lieutenant commander Philippa Georgiou at the New Anchorage hospital. Georgiou offered to help repair the damage to Shannon's stuffed Andorian toy Vran. Shannon wound up giving the toy to Georgiou.
Following the massacre, Shannon and her mother left Tarsus IV. Trying to understand what had happened on Tarsus IV, Shannon decided to write The Four Thousand to help her and other young survivors better understand what had happened. For her book she interviewed people on both sides of the conflict, both survivors and supporters of former Governor Adrian Kodos. Many people were quite willing to talk to Shannon, however some people like Captain Gabriel Lorca declined requests for an interview. Before her illness and death Shannon's mother also sat down for an interview with Shannon for the book.
Shortly after finishing her book, Shannon visited Captain Georgiou on board the USS Shenzhou to give her a copy of the book. Georgiou was quite impressed with the book. During the visit she revealed that she had kept Vran all the years since the massacre. (DSC novel: Drastic Measures)