This discussion may contain spoilers!
This is a topic where people can list random theories about the game..
My first is the following... I think the pig from his apartment is the serial killer. He voiced to the pig that he helped that girl.. Showed interest in her.. BANG! pig gone.. Girl dead.. He also knew that he liked snow.. It seems this killer is targeting people Bigby cares about.. It is personal.. And that pig shows up right when the killing starts? Coincidence?? I think not! He acts like he cares about bigby.. That the past doesn't matter.. I totally think it is the pig.. I could list about 3 other things which grant weight to this opinion, but yeah.. As for the whole looking like a pig.. Cutting of heads and such.. Glamour?? Makes em look human, yeah? I mean a frog can drive a car, so.. Plus he was sent to the farm.. Had to escape or w/e.. Maybe blames bigby for letting him be taken.. Also the whole house thing, his brothers, etc..
Just a theory