What I keep coming back to is: It's pretty uncommon that there was a hatred so intense and so personal that someone shot her down in her driveway (and made sure to tell her why before doing it), but at the same time, so easily hidden that nobody who knew Liz seems to have any idea who'd want to do this. Even if the person who shot her isn't the person who wanted her dead, even if this is some weird hitman (or hitwoman) situation of some sort, it's baffling to me that whatever set it off isn't known to anyone who knew her, or if it is, they're not talking. That degree of hatred suggests a level of interpersonal entanglement that usually leaves signs, even if the signs are just holes in a person's schedule. Awfully strange.