The How to Get Away with Murder promos weren't lying with that ominous "not everyone is going to make it out alive" tease.

The final minutes of Thursday's premiere revealed the "game-changing" Season 3 mystery, and yup, someone is dead. A flash-forward shows a frantic Annalise (Viola Davis) running to an ambulance, demanding to see the covered-up body on the gurney. The paramedics show it to her and she breaks down sobbing, while the shot pans wide to reveal her house up in flames. Yeah, it's less a whodunit and more a "who is it?" this year.

"I'll tell you at this moment I still haven't figured it out," creator Peter Nowalk tells TVGuide.com of the twist. "We're just going episode by episode. This major mystery is probably the most serious one we've done yet."

How to Get Away with Murder's Season 3 mystery is the "most game-changing one yet"

The identity of the body is likely to be someone in Annalise's inner circle, given that Season 3 is designed to be, as Nowalk describes, "very personal." "It's both new and it's tied to the past. For me, what I've tried to do — sometimes successfully, sometimes not — is to always make sure all the pieces are connected, that all the dominoes are interconnected and run into each other," he says. "I think it's definitely tied with the stuff that happened the first season and even the discoveries that happened 10 years ago when Annalise lost her baby — how all of that set in motion this inciting incident right now."

Viola Davis, How to Get Away with MurderViola Davis, How to Get Away with Murder

The most obvious choice is Frank (Charlie Weber), who's now clean-shaven and rocking a buzzcut — and as we last see him, about to kill the man Annalise has tailing him. Annalise hesitates putting the hit out on Frank, and we are supposed to learn more about their backstory this season.

"We're going to find out when Annalise and Frank met. I've always been wanting to tell Bonnie's (Liza Weil) and Frank's origin stories and I think we dribble things out. We're going to answer a big question this season," Nowalk says. "I think there's going to be both OMG moments and emotional moments. That's really about digging into the psychological struggle of the characters. ... The flash-forwards are going to be very shocking as the episodes go on and you learn more."

Unlike last year, when Annalise's shooting was connected to the prolonged Hapstall case, Nowalk says that this year's is more contained for maximum fan investment.

"I think the most exciting thing about it is that the focus is back on the people we know," he continues. "I think that's very important. These people are bonded through these terrible acts and it's always a push-pull of who to trust and suddenly it's 'How did we get here?'"

How to Get Away with Murder airs Thursdays at 10/9c on ABC.