King explained that the show has already revealed some clues about who the mysterious figure could be.
"'A' is a peeper, 'A' is always spying on people," she told The Hollywood Reporter.
"'A' has some money because 'A' stole the money from Ashley and Hanna, so 'A' has access to cash. 'A' has access to a lot of surveillance. Ultimately, when we find out who 'A' is, that all will make sense."
King also teased that the identity of Alison's killer will be revealed before viewers find out who 'A' is, saying: "It may or may not be [two different people], but somehow they could be connected."
She added: "Somebody wants to torture these girls for a reason so I think it will be a very satisfying answering when that answer comes out."
The second season of Pretty Little Liars continues on Tuesdays at 8/7c on ABC Family.
> 'Pretty Little Liars' exec expects four seasons