'Only Murders in the Building' Season 4 ending explained: Who killed Sazz and why?

That's a wrap on a very Hollywood-themed Season 4 of Only Murders in the Building!

After 10 episodes of A-list cameos, stunt man shenanigans, and the highs and lows of showbiz, Charles (Steve Martin), Oliver (Martin Short), and Mabel (Selena Gomez) finally caught Sazz's (Jane Lynch) killer. But in true Only Murders fashion, it's not long before another body drops, setting the stage for Season 5.

From catching our killer to theorizing about what comes next, let's break down that finale, spoilers and all.

Screenwriter Marshall P. Pope killed Sazz Pataki — but not for the reason you think

Like every season before it, Only Murders Season 4 is no stranger to red herrings. After all, the entire West Tower storyline ended up being an elaborate misdirect, while actors Eugene Levy, Zach Galifianakis, and Eva Longoria's theory that that this murderer had been after our trio since Season 1 also turned out to be false. But in its penultimate episode, Only Murders Season 4 hit us with a softer red herring — one concerning Sazz's killer's motive.

At the very end of episode 9, "Escape from Planet Klongo," Charles, Oliver, and Mabel learned that Sazz's killer was none other than Marshall P. Pope (Jin Ha, Pachinko), the screenwriter of the in-the-works Only Murders movie.

Marshall, whose real name is Rex Bailey, was Sazz's stunt protégé — at least, he was until he burned director Ron Howard's eyebrows off in a stunt gone wrong on the unfinished film Project Ronkonkoma. Sazz blackballed him after that, replacing him with stuntman Glen Stubbins (Paul Rudd), which is why the Only Murders trio thinks Marshall murdered her. Turns out, his actual motive was to get away with stealing Sazz's screenplay for the Only Murders movie.

Why did Marshall kill Sazz and Glen?

As Sazz tells us in voiceover at the start of the finale, decades of stunt work was taking a toll on her body, and she wanted to find another way to contribute to bringing stories to life. That's why she wrote the Only Murders script, centered on her "hero," Brazzos himself, Charles-Haden Savage. Sazz brought it to Marshall, hoping to get some pointers from the other aspiring screenwriter she knew. However, his jealousy over how good her script was prompted him to disparage it, then steal it and sell it to Bev Melon (Molly Shannon) as his own. His biggest crime really was plagiarism. Just kidding, it's still murder, but this is a close second.

From there, Sazz heads to New York to tell Charles about the movie she'd written. Again, nothing here about the Westies or their involvement with Dudenoff (Griffin Dunne), just good old-fashioned Hollywood drama.

Sazz did write a Dudenoff subplot into her script though, which is how Marshall knew he could get into the West Tower of the Arconia and snipe her from Dudenoff's now sadly empty apartment. (His pitch-perfect aim is a result of a traumatic childhood of being forced to hunt by his father, the basis of his unsuccessful first script.) Once he shot Sazz, he made it to Charles's apartment by creeping along the window ledge going around the Arconia's courtyard. Being a physically fit stuntman who isn't afraid of heights sure has its perks! From there, he disposed of Sazz's body down the trash chute where the incinerator awaited, with the whole endeavor taking less than 12 minutes.

Later, when Marshall realized stuntman Glen Stubbins could identify him from their overlap on Project Ronkonkoma, he tried to take Glen out with the same sniping method during a promotional photoshoot — where he accidentally shot Galifianakis as well (both survived). With Glen on the mend in the hospital, Marshall went to his ward to finish the job, so the connection between his new identity and his old one would remain concealed.

In Mabel's apartment, Marshall confesses all of his crimes to Charles, Oliver, and Mabel before trying to kill them, but not so fast! In a reversal of Sazz's murder, Marshall gets shot through the window from Charles's apartment. The culprit? None other than Jan (Amy Ryan), who's been living in the Arconia's secret passageways for months and finally saw a chance to avenge her beloved Sazz (and simultaneously save her former beloved Charles).

Sure, the cops arrest her, but when has that stopped her before? You can bet this isn't the last we've seen of Jan. After all, she asserts that she and Charles are endgame. What is this, Riverdale?

Oliver and Loretta's wedding goes great — until we learn that doorman Lester is dead.

Thankfully, some less deadly love is in the air at the Arconia in the form of Oliver and Loretta's (Meryl Streep) marriage. It's a lovely affair, complete with Oliver's dog Winnie serving as ring-bearer and Loretta's son Dickie (Jeremy Shamos) and Oliver's son Will (Ryan Broussard) walking the bride down the aisle. The only downer is that Loretta is moving to New Zealand to shoot the rest of her TV show. She tells Oliver to stay in New York though, because when has their relationship ever been conventional? And how else to give Streep an easy out if she's not up to return for Season 5? (Although I'd love to see her come back.) Or, hear me out, the gang goes to New Zealand next season for a Lord of the Rings-themed mystery.

Aside from Loretta's moving announcement, the wedding goes off without a hitch. But after the celebration, Charles, Oliver, and Mabel discover the corpse of doorman Lester (Teddy Coluca) in the courtyard fountain, continuing the Arconia's streak as the deadliest building in New York.

Lester hasn't been around much this season, but he did pop up towards the start of the finale episode to tell Oliver and Charles an interesting anecdote. He tells them he got married in the courtyard too. He'd shared: "Middle of the night, with just the stars and the fountain as our witness. I think it's good luck!"

Sadly for Lester, his luck ran out. (Oliver even foreshadows his death in their brief encounter, complaining that, "All [Lester] does is let in murderers!") But perhaps Lester's description of the marriage ceremony is a clue for next season. Speaking of next season...

Who is Téa Leoni's Sofia Caccimelio?

Another clue for what Only Murders Season 5 has in store is the arrival of the mysterious Sofia Caccimelio (Téa Leoni, Madam Secretary), whom Charles can only describe as a "dame."

As she tells Mabel and Charles, her husband Nicky was recently reported missing, as seen on news report playing on a hospital TV in episode 9. The report described Nicky as "the dry cleaning king of Brooklyn" and mentioned his ties to the Caputo crime family. Despite this, police say they don't suspect foul play. Sofia thinks otherwise, asking for Charles, Oliver, and Mabel's help find her missing man.

When Charles and Mabel tell Sofia they aren't private detectives and only investigate Arconia-related murders, Sofia drops a bomb on them: "What happened to Nicky has everything to do with this building." What new secrets does the Arconia have in store? And could Nicky's disappearance be linked to Lester's death?

We'll have to wait for Season 5 to find out.

Only Murders in the Building Season 4 is now streaming on Hulu.