Only Murders in the Buildingexecutive producer and showrunner John Hoffman explains the reveal of Sazz’s killer in season 4. Premiered on August 17, the latest season of Hulu’s murder mystery series follows the podcasting trio – Charles, Oliver, and Mabel – as they investigate the death of Sazz, as revealed during theOnly Murders in the Buildingseason 3 ending. After nine episodes of intrigue, season 4’s penultimate episode reveals that Sazz’s killer is the screenwriter Marshall, who is actually Rex Bailey, her stunt double protégé on the set of Project Ronkonkoma.
During an interview withThe Wrap,John Hoffman explained the reveal of Sazz’s killer inOnly Murders in the Buildingseason 4, episode 9. The executive producer and showrunner says the decision to make Marshall/Rex the killer was made from the beginning, allowing them to work backward from that conclusion. He also highlights how several clues, such as Sazz’s ham radio in season 3, were deliberately planted to connect to the cold case in season 4. Read his full comments below:

Day one. This has evolved because it wasn’t the case in Season 1. We had various possibilities for the killer in Season 1 when we started the writers’ room. But ever since then, we have to work backwards or just figure out the end and everything that really happens around the incident that caused the murder, so we can’t really go anywhere with writing until we have that and then twist our way to it. So that was all figured out right at the beginning.
When we were shooting Season 3, we very purposefully put in the moment in Episode 5 where she’s talking about her ham radio to Charles and saying there’s some chatter “I’m picking up that people say they wanted to be you” so that when what happens at the end of Season 3, we would have made some connection.

At the end of Season 3, when she brings in her cold case, it felt like that was one of those lovely things that happen in the writers’ room when you realize, “What does she have in that cold case that they don’t know about that’s been sitting in Oliver’s refrigerator the entire season and holds really the key clue to everything Sazz started and what she was needing to talk to him about for months that now had to be rushed?” So all that felt exciting to me as a clue that could make you go what the hell by the end of it all and then also the dance of hiding it as best we could.
The emotional relationship that we explore and reveal in Episode 10 between Sazz and Rex is meaty and, in general, lines up with exactly all of the clues that we’ve laid out across the season as to how and why that all happened.
What John Hoffman’s Comments Mean For Only Murders In The Building Season 4
Several Clues Were Planted
John Hoffman reveals the decision to make Marshall/Rex the killer was made from day one of the writing process forOnly Murders in the Buildingseason 4. For the first time, the writing team worked backward, figuring out the ending first and weaving the clues and storyline together toward the conclusion. This includes laying the groundwork for Sazz’s murder byincluding clues that would later connect to the reveal in season 4. For instance, Sazz’s comments about hearing chatter on her ham radio in season 3, episode 5 were planted to foreshadow the events leading up to her death.
Only Murders In The Building Season 4, Episode 4 Ending Explained: Is THAT Sazz’s Killer?
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During season 3’s ending, Sazz’s cold case also hinted at deeper clues that would be crucial in solving her murder. Rex Bailey, who was Sazz’s stunt double protégé on the set of Project Ronkonkoma, was involved in a fire-related incident that ended up singeing director Ron Howard’s eyebrows. Then, Rex seemingly killed Sazz andstole her script for theOnly Murders in the Buildingmovie, which was hidden inside the case of beer she had been carrying around.
Our Take On The Upcoming Only Murders In The Building Season 4 Finale
There Are Still Several Unanswered Questions
While season 4, episode 9 revealed that Marshall/Rex is Sazz’s killer,several unanswered questions remainfor the upcomingOnly Murders in the Buildingseason 4 finale. It remains unclear how he was able to kill Sazz within just 12 minutes. Additionally, it’s unclear if the killer worked alone, or if he had accomplices. These lingering mysteries, and much more, should be addressed in theOnly Murders in the Buildingseason 4 finale.
TheOnly Murders in the Buildingseason 4 finale airs on October 29.
Only Murders in the Building
Cast
Only Murders in the Building is a mystery-comedy series following three strangers, portrayed by Steve Martin, Martin Short, and Selena Gomez, who bond over their shared obsession with true crime. Set in a Manhattan apartment building, the trio becomes embroiled in a real murder mystery within their residence.