The Star Stone from the crime scene should become an inert stone after you approach it.
If you do have 4 inert stones, enter the Inner Chamber again (go far enough to get the cutscene conversation with a demon, if you have not done that already) and then return to the main section of the homestead with one of your main characters selected as leader. That should get Zixzax to head over to the statue, if you have enough used star/blood stones.
