The shooter would have had to have knowledge of the garage sale. The driving by in the early morning hours before makes me think they had not been there before and wanted to get a lay of the land, so to speak, or plan their escape route. They could have killed her as she left for Starbucks, but the timing of it was predetermined. Why? Knew she would be outside for the garage sale? Wanted to ensure Sergio was gone which would require knowledge of his schedule as well? Both? This case is infuriating!
Also, I think they quickly moved from Goddard school because they didn't account for parents to be dropping their kids off that early. There would have been a much greater chance someone took note of a truck just sitting there. According to the Goddard School website they open at 6am. The timing of the whole thing really baffles me.
All speculation, of course.