Ah, I see what you're saying now. I wonder if it was typical/usual that she might come back earlier from a family vacation? I mean, would it be someone who would be more likely to go to the house thinking that it would be completely empty because the family always came back from vacation together? Or someone who would be more likely to know it would be just her, because she routinely came back ahead of schedule?
Like many of you, my mind jumps to wondering about the husband, just because it seems a bit too convenient that she was in the house alone, while he would have the perfect alibi (*her* family, even. You could see *his* family lying for him...but hers? In a hypothetical case where he was the POI, of course). But I also agree that a hammer (if that is indeed what was used) just seems like a weapon of opportunity. Has there been a case where someone's premeditated weapon of choice was a hammer? I know a murder can count as premeditated in just a few seconds. But I mean a case where someone deliberately packed up their favorite killin' hammer before going on the prowl?