'Scream 6' Ghostface killer initially thought they were playing a different character because the villain was 'written so mildly': 'It was me all along'

• Warning: Major spoilers ahead for "Scream 6."
• The actor behind Ghostface in "Scream 6" initially thought they were playing a different character.

Sam (Melissa Barrera) and Tara Carpenter (Jenna Ortega) may have survived "Scream 5," but Ghostface isn't done with them yet. A brutal new killer targets the sisters and their friends after they move to New York for college in "Scream 6."

But the actor behind Ghostface said they thought they were playing a completely different character when they first read the script.

As revealed in the final act, Dermot Mulroney's Detective Wayne Bailey is the mastermind behind this latest killing spree, as he wants revenge on Sam for killing his son: Richie Kirsch (Jack Quaid), one of the killers in "Scream 5."

The actor explained that he was only told he was "the bad guy" when he got the role.

"It wasn't called 'Ghostface' there; it was just 'the bad guy.' I wasn't even up on how intense people are following Ghostface," Mulroney said.

The "My Best Friend's Wedding" and "Zodiac" star noted that he wasn't told who he was playing when he was given chunks of the script, so he was trying to figure out who the killer was.

He recalled: "So then I get pieces of the script, but they neglected to tell me what part I'm playing. So I'm looking for two things when I'm reading the script, which part it is that I am and who it is in the script that's going to wind up being Ghostface."

Mulroney said that he suspected he was going to play Sam's psychologist, Christopher Stone (Henry Czerny), and didn't even consider Detective Bailey because of the way he was written.

"So, for a while, I suspected that I was going to play the psychologist because Bailey is written so mildly I thought that's probably not my part; it's just a passing detective. It shows you that the script itself was quite ingenious in how they buried Bailey or made him incidental to scenes. Then I get to the end, and it is Bailey! It was me all along!"

The final act sees Bailey unmask himself as the killer alongside his children Quinn (Liana Liberato) and son Ethan (Jack Champion), who all want to avenge Richie's death.

According to Mulroney, filming the final act was "glorious."

"It was glorious. It was glorious, and all of us were in a great mood because it's that moment in the movies," he said.

"Scream 6" is in theaters now.