Suspects ? Spoilers
Annika Melander is the latest but I suspect that she has a partner.
I have a hunch that the owner of the shipping company, who although played by a prominent Scandi actor, has had almost no screen time, will come to the fore.
I can't yet work out a connection between him and the "stalker from hell" Annika, nor why the murders are replicas of some of Freddie's paintings.