IMHO, the most likely of several possibilities is this.
The perp is local and has known Holly for at least 6 months. Evedince is that he went to her house. That is both local and personal. Other options would have been centered around the school campus.
Holly had some previous level of fear of the perp. Evidence is that the perp did not drive down the driveway. Holly would have taken some alarming or evasive action. Other evidence is an assumption that the perp had to approach Holly concealed because Holly would not approach the perp.
The perp did not know her brother was home until he was at the house. Evidence is an assumption that he wanted to perp Holly in the house.
If the perp wanted to sexually and/or physically abuse Holly in the house, then he perped her in the woods. Either her body is still there (which I originally thought true but now don't) or is in woods or water within 20 miles. Assumption is that the perp is local and finds refuge in woods and/or water as a good hiding place.
If the perp wants Holly as a possesion (and let's all pray this is the case!), he has hidden her in a remote trailer or house (lesser possibility is a hunting cabin). Assumption is that the perp is not employed and therefore can leave for short periods of time and participate in life but still focus time on Holly.
Whew, that was a long post.