I'm sure LE is looking into the creepy bus driver theory. When going through that specific bus route, I realize the driver would be able to see all the patterns in the area and know who is usually doing what and where in the early mornings (and even afternoon as he is now doing the PM route). Could have noticed the farm hands M.I.A. every friday. Could have noticed where street cameras were located, etc.
It would have been entirely possible for anybody to park at the end of the cul de sac without being spotted by a neighbor. The closest house with the BEST view of Sierra's home was up for sale and vacant. Perp would have noticed that detail IMO. I imagine perp could have parked up at the end of cul de sac. The little dogs that yap in the yard near her driveway wouldn't be much of a deterrent IMO. She would not have a great view stepping out of her front door to any potential danger hiding around the corner. There is an exterior part of her house that blocks her view of the other side of the garage as she steps out her front door. Somebody could have been lurking in the driveway... taser/stun gun? Would there even be a scream? Scary thought.
The placement of the purse was perfect... quickly accessible from scene of crime, no cameras, nobody usually around on that road, perfect long line of sight in both directions where you could time it right (the placement) when no traffic on Santa Teresa, out of plain sight but somewhere it would be found eventually by police/searchers.
No way in my mind this is a crime of opportunity. Especially if she didn't make it past her drive way/few steps past front door area. Odds are slim to none that a freak capable of pulling something like this would be in that place at that time on that day without having somewhere to be. IMO.
No signs point to a gang related crime. No signs pointing to a random crime of opportunity. Most signs point to a carefully calculated abduction who knew the area well. Which is scary.