Pretty Little Liars showrunner Marlene King doesn’t want us to get any sleep! Hot on the heels of a spoiler that someone is going to die in Season 3, Episode 21: “Out of Sight, Out of Mind,” she tweets this unsettling tidbit at an unsuspecting fan:

“Working hard on Season 4. It's gonna be KILLER.”

Oh no! Could this death have something to with the aftermath of the Season 3 finale? Marlene has already dropped several hints at a fire or explosion in Season 3, Episode 24: “A Dangerous gAme.” PLL season finales usually end with a bang, leaving us waiting until the following season premiere to find out the repercussions to our Liars’ lives. Perhaps this death is connected.

There is also another way to take the “killer” hint. Maybe one of our favorite Rosewood residents is not the victim, but the killer herself. Obviously, that still means someone bites the dust, but it might not be quite as heartbreaking. Then again, Emily (Shay Mitchell) has not had an easy time dealing with killing Nate in self-defense earlier this season. Sometimes, these girls are as haunted by what they’ve done as by what is done to them.

We suppose we can take some small comfort in the fact that Marlene is working so hard on Season 4. With filming starting up in March, we won’t have to wait too long to see our girls back in action...if all of them make it, that is.

What do you think Marlene means by her “killer” tweet? Are you worried about the Liars, or do you think someone else is in danger? Let us know in the comments below!

Catch the next episode of Pretty Little Liars on Tuesday, February 26, 2013 at 8 p.m. ET/PT on ABC Family.