The following contains spoilers for Only Murders in the Building season 4, episode 10.Only Murders in the Building showrunner breaks down Marshall’s (Jin Ha) backstory and how he becomes the first murderer to be killed off in the show. Marshall is first revealed in the show as Sazz’s murderer in season 4, episode 9. The season finale dives into his entangled past with Sazz and how he eventually finds himself in the position of a murderer. At the episode’s climax, Jan shows up and shoots Marshall the same way he killed Sazz, shaving Mabel, Oliver, and Charles’ lives.

https://screenrant.com/only-murders-in-the-building-season-4-ending-marshall-killer-backstory-explained-john-hoffman/