[Spoilers for the Season 1 finale of Riverdale below.]

Something wicked this way comes to Riverdale. The show's Season 1 finale ("Chapter Thirteen: The Sweet Hereafter") had a little bit of everything — a secret brother reveal, a suicide attempt, teen-sex shenanigans, and a performance from Archie Andrews and the Pussycats — but the most devastating (and game-changing) moment happened during the episode's heart-pounding final moments: Fred Andrews was shot in cold blood by a masked hitman at Pop's.

Oh, and Archie was there to witness the whole thing.

MTV News talked with showrunner Roberto Aguirre-Sacasa about going "darker" in Season 2, giving Archie a Bruce Wayne–style origin story, and how the shooting is just the catalyst for the "civil war" to come.

MTV News: I can't believe you shot Fred Andrews!

Roberto Aguirre-Sacasa: You know, it's intense. It's really intense.

Was that always the plan? Or at what point did you know that this was how the season was going to end?

Aguirre-Sacasa: It was not always the plan. It came very, very late into the season. We knew we wanted to end with a huge cliffhanger, and for a while, we thought that it would be Hiram's arrival. But when we really thought about it, it was like, We don't know Hiram. People aren't that invested in Hiram yet, and we wanted this to be powerful. So we started talking about what relationships people were really invested in, and one of them is Archie's relationship with his father.

When there's so many fractured families and characters with dark motives in Riverdale, it was nice that there was one where the love really is unconditional — and it's true and it's deep. We felt like, What would happen to Archie if that went away? And what would happen if he saw his worst fear, Fred get shot in cold blood, in front of his eyes? It became terribly inevitable, then, that Fred, the guy who has always believed in Riverdale and whose hands are cleanest, is most touched by the darkness that's swallowing Riverdale.

Will we know Fred's fate very early on in the second season? Because I know you guys are currently plotting it all out in the writers room.

Aguirre-Sacasa: We will learn about Fred's fate in the premiere of Season 2. This is such a huge moment for Archie. It really is his origin story in the same way that Bruce Wayne's parents getting shot before his eyes in Crime Alley is what made Bruce Wayne become the man he was going to be. Or when Peter Parker learns about his uncle Ben's death at the hands of the burglar, and he says, "I'm going to be a hero." That's kind of what happens to Archie in this moment, and we have to really play the aftermath of that in the premiere.

It will also make Archie more proactive in Season 2, right? He's not the same Archie who plays love songs on his guitar and chases girls at Riverdale High.

Aguirre-Sacasa: For sure. Gone are the days when Archie's trying to decide between football and music, and gone are the days where Archie loves Miss Grundy and then he loves Valerie and then he might still have feelings for Betty and then he's kind of crushing on Veronica. That's behind Archie. And he's absolutely at the heart of the crime that starts a big civil war in Riverdale.

Is the central mystery for Season 2 who shot Fred Andrews?

Aguirre-Sacasa: It starts there. It very quickly proliferates, though. But it absolutely starts with that. Then again, there are secrets within secrets and motivations behind motivations, so it does expand. But it starts with who shot Fred Andrews?

The other big reveal of this episode is that Betty has a brother. Can we expect him to pop up in Riverdale at some point?

Aguirre-Sacasa: When you do things like mention a secret brother, which is so soapy, I think you have to introduce that character. Hopefully, you can introduce them in the most dramatic, unexpected way, which is what we're possibly going to do with this guy.

But will it be Chic Cooper [Betty's brother from the comics] or someone else?

Aguirre-Sacasa: It takes a real, die-hard Archie fan to know that Betty has a brother named Chic Cooper. So if Betty has a secret brother, it might have something to do with the Chic Cooper from the comic books. Maybe!

Let's talk about one surprise introduction that did happen toward the end of the episode: Hot Dog! I know Hot Dog's casting was a huge point of contention for you and Cole Sprouse.

Aguirre-Sacasa: Listen, that was all Cole. He really wanted Hot Dog. He really wanted a sheepdog to play Hot Dog. He was really passionate about that. It was very hard to find a sheepdog in Vancouver who could deliver all of the nuance that Hot Dog required. It all happened at the last second. Basically, when we got the dog, I said to Cole, "We're going to try and make this work, but if this dog comes in and he can't deliver as Hot Dog, we're just going to do the scene without Hot Dog." And he was like, "That dog better deliver." And the dog did great! You'll be seeing more of Hot Dog in Season 2 for sure.

Cole must be a real stickler when it comes to the Archie canon.

Aguirre-Sacasa: In a way, Cole is even more of a purist than I am, especially when it comes to Jughead and the Jughead mythology. For me, I was like, "I don't know if the Serpents are going to have a sheepdog. He's more like a junkyard dog. TV adaptations reinvent stuff all the time." And Cole was like, "Fine. But you're not reinventing Hot Dog." He had a really good point. Cole is an artist. He's very passionate, and I'm glad Hot Dog is a sheepdog and that he's now in our universe.

Jughead kinda became a Southside Serpent in this episode. There's this great moment when he's putting on his Serpents jacket, and Betty is giving him this look like, "Who are you right now?" How is this going to affect their relationship in Season 2?

Aguirre-Sacasa: That moment in particular certainly provides a lot of fodder and tension for them. We really think of that moment as the end of The Godfather when Diane Keaton is looking at Al Pacino, Michael Corleone, being surrounded by the Mafia family and she's on the outside looking at him. That's what we think of when we look at them. That's also a mythic moment in the Bughead mythology.

Betty spends a lot of this episode defending the Serpents, but in that moment you see that maybe she's not as cool with Jughead's affiliation with them as she thought she was.

Aguirre-Sacasa: Between Jughead going to a new high school, Jughead moving to a new part of town, and Jughead following in his father's footsteps, I think any one of those things Betty could maybe shrug off. But all of them? And knowing that Jughead has always felt like an outsider in her circle? I'd be worried, too.

It couldn't just end with them saying "I love you," could it? There had to be drama.

Aguirre-Sacasa: This is Riverdale. There's never a happy ending [laughs].

But is there a limit? You're also the chief creative officer of Archie Comics, so I wonder how far you can push things in Riverdale.

Aguirre-Sacasa: Jon [Goldwater, Archie Comics CEO] is such a good partner to us, and he obviously knows everything that we're doing on the show. He's often the one who's encouraging us to push further. I hope the show never becomes a nihilistic, fatalistic version of the comic books. I always want there to be a balance of darkness and light. I want there to be tension. Season 2 is going to be tipping more toward the darkness, and the struggle to avoid that is going to be more difficult.

Finally, I'm curious about Jughead's narration. He's going to continue narrating Season 2, right?

Aguirre-Sacasa: Yes.

How far into the future is Jughead narrating this story?

Aguirre-Sacasa: It's a little bit of dramatic license, sort of like the stage manager in Our Town. He's our Rod Serling. He exists out of normal conventional time. He could be doing it from many different time periods. We tried to really be specific about that for the first couple episodes, and then it was like, "You know what, guys? Just go with it."