I don't see it so black and white. There are many scenarios. For instance, he could be out of town, planning to target someone with the means to do it and looking around for a target, then sees her and carries it out (with what he has with him already). He could be from out of town and driving around and acts impulsively without the full plans ahead of time , not planned means to do it, etc. He could be in town and been watching her and planned how he will carry it out one day completely or he could be in town, fantasizing, then act impulsively when he sees her this day on a whim (without so much exact planning). He could know her through association, even having talked to her before in some prior activity or run in somewhere. He could know of her by only seeing her in the area. He could not know her or know of her at all. This is the issue. The scenarios go on and on which is what LE narrows down. Yet, we do not know what they have, so it leaves this very open to numerous possibilities.
**However, IMO - I agree with Joshua the fire was likely to remove his DNA, ***especially because a struggle was reported***, so specifically 'after' the struggle occurred and he knew his DNA was left behind. If he knew he is not in the 'system' yet, it points more to someone in the town being worried of the connection still being made compared to someone outside of the area who can take off and they may never make the connection.