[Christen]

This talk of Battler's killer gave me an idea, but it's still farfetched due to Eva's dialogue.

Spoiler for Eva's dialogue:

"You've just noticed now, Battler?"

..or something like that. It just shows, Eva was talking to Battler before she shot him. Battler did indicate the he figured out that Eva was the culprit (of some of the murders of course, but not all of them. Though I doubt Battler thought of it like that.).