I'm a new member to the Websleuths community, although I've followed a few threads in the past for cases which caught my attention. I was compelled to register and post here after seeing the footage of this poor woman's murder on a news site. To me, this case is really simple once you break it down-
If you accept that this was a targeted murder and not some crazy person committing a random violent murder in the early morning hours in suburbia, then "whodunnit" boils down to one simple question:
Did the killer know about the garage sale? If the answer is yes, then that greatly narrows the suspect pool due to the fact that the garage sale wasn't advertised publicly until that morning.
It seems highly probable due to the timing of the killer's arrival occurring just after the husband's departure that the killer intentionally waited until the husband had left for work. There are multiple reasons why that could be, and I won't speculate on that. But then, one of two things happened. Either the killer: a) showed up to murder EB, unaware of the garage sale, planning on murdering her by ringing the doorbell and shooting her or perhaps sneaking into the house to commit the crime, or b) showed up to murder EB, knowing full well she would be in the driveway setting up the garage sale.
If it's scenario a, then the killer could be just about anyone connected to her, her husband, her family, or her ring of social acquaintances in some way... anyone from a co-worker who secretly harbored an unrequited crush for years, to a business associate of the husband seeking to hurt him by killing her, to someone involved in the Star Wars group who took fantasy too far, to something more sinister closer to home.
But if it's scenario b, as I said above, I would think the suspect pool would be limited to only people very close and possibly co-workers.
The last thing I'll say about this case is what I took away from the video. Apart from the observations which have already been made here, I noticed that the killer seemed to pause for a short time (maybe 5-10 seconds) after putting the truck into park before exiting the vehicle to commit the crime. Was that due to something as simple and likely as the killer doing a quick check around for possible witnesses? Was he/she steeling his/her nerves to go ahead with the plot? Or was the sight of her right there in the driveway enough of a surprise to give the killer pause (like perhaps in scenario a where he/she had no idea a garage sale was happening)?
Also, when I first viewed the video, I thought I saw what were definite white/cream knee-high boots and a white/cream robe on the killer. I'm not even a huge Star Wars fan, nor had I read about any connection to a Star Wars cosplay group at that point, but I immediately thought of the outfit Daisy Ridley's character wore in the movie. I'm glad to see that others here thought the same thing too.
I'm 50/50 on the killer's gender, 50/50 on the motive (either passion-related or financial/job-related), but I'm about 99.9% sure the police are already on to their suspect and are just gathering enough evidence to convict at this point.
I just feel awful for EB, knowing she was killed going to extra lengths so she and her husband could enjoy a wonderful anniversary trip.