yeah, after poking around in the street view, I'm leaning toward the house being stalked/targeted in advance. It was more isolated than first appeared, because the house next door was vacant and there's a big back parking lot for the strip mall that abuts the backyard and side fence. Between the lot there and the one across the street (which I believe I read was built for a school/college of some sort at the time ?- I'm sure someone here can tell us what it was) there's a lot of places he could have parked a car and hung out to scope out the property over a period of days or hours without being terribly visible or looking particularly out of place.
I wonder if he might have pulled in the drive right next to the fence and then walked them out beside the fence from the front door. I don't believe there was an entrance from the their carport overhang, just two large windows based on watching the 48 hours video that was included a walk through of parts of the house with a few days of them missing.