OK, let's recap what we know so far. Obviously LE knows much more info (which could help us choose among theories) and isn't sharing all of it. It seems to me that the most likely scenario is the perp was after Jayme. So the possibilities are 1-stalking/pre-planned; 2- spur of the moment (followed home); and then either 3- broke in house around 12:30, or 4- was already in house when dad arrived home (would be good to know when that was). Without knowing more about the damaged door evidence, and where bodies were, it's hard to say which of #3 or #4 it was. Dad near the door could be from him coming in and being shot (door shot up from inside then), or answering the door in the middle of the night and immediately getting shot.
I am discounting the possibility of online catfishing because if that was the case, LE would have already checked social media, Jayme's friends, etc and have very good leads. And doesn't fit with description of Jayme's personality, as also noted by other commentators.
The news article said that the phone had a VOICEMAIL (when dispatch called back) stating it was Denise Closs' voicemail. So it's likely that it was Denise's phone, and Denise was still alive, and valiantly made the call. It could be the perp was busy with Jayme, heard something (such as 911 operator saying "what is the nature of your emergency?"), went to find phone, possibly destroyed it, even polished off Denise maybe (accounting for why live parent was dead 4 mins later), and realized he had about 2 minutes to get out of there---so grabbed Jayme and went. (Most kids that I know don't know how to work mom's phone if it is password protected.) Although a second possibility would be Jayme made the call (perhaps while claiming to go to bathroom or something) and then left the phone somewhere so perp wouldn't know---she obviously couldn't speak to them without warning him. Perp must somehow have figured it out (see above ref maybe hearing dispatcher) and ended the call. Maybe the perp intended to stay in the house, have his way, and eventually murder Jayme too but something happened (she went to bathroom and secured phone? Denise managed to make a call herself?) that suddenly required a change in his plans. If the latter, he wouldn't already have a place ready to take Jayme.
A curious thing is the "evidence" chair that looked like someone had been tied to it. Who was that person? Presumably Jamie --maybe to control her? Or could it have been Denise? Torture or what? Needed some kind of information? Just waiting for dad to get home? Didn't know dad was coming? Seems unlikely he wouldn't know dad's schedule, if it was pre-planned. If someone from dad's work, would surely know. (Lots of questions....) Agree with other commentators on the curiosity of perp remaining in the house for 20+ minutes. You'd think he would just grab Jayme and go. This makes me think that he might already have been in the house, with the two women, when dad arrived home. If the crime scene was horrific, seems there must have been more than just boom-boom two gunshots going on.
When the LE said they have "100% expectation that Jayme is still alive", wonder what that was based on? Another commentator noted number repetition (100 pounds, 100% expectation, only 100 volunteers needed) and I noticed it also with "200 LE on this case", "200 tips" etc. Wondering if this is somehow messaging, and if LE has received unknown comms from the perp.
Another curiosity is neighbor heard 2 shots, yet the deputy reported several spent rounds---not just 2. Anyone have any thoughts on that? Maybe there were earlier shots too and the neighbor just didn't hear them. 300 feet is a long way away---the neighbor didn't, for example, hear the yelling that the dispatcher reported.
It doesn't seem random, and it seems like acquiring Jayme was the primary motive, accounting for why she wasn't killed. it was a small house, so spiriting her out might have seemed impossible, whereas killing both parents seemed "surefire" to the perp? I'm voting for either "caught someone's eye who followed them home from party" (like the Petit case) or, seeming to me much more likely, Jayme had a stalker that planned this out---and so is likely to be local. Maybe even thought about it for a long while. Could be pretty much anyone in town, starting with the painters from 2 years ago but anyone that she had caught his eye. I agree that if they ask for DNA the perp won't show, but that would also be telling. And as others have pointed out, if he left ANY DNA behind, familial matching is possible these days.
And to respond to an earlier question---news sources stated that these two were both Jayme's biological parents. There can always be deep dark secrets lurking in anyone's life though. I'm sure the LE are looking at financial records, phone records, etc to identify if the parents were targets for some reason. But sure looks to me like the target was Jayme.
So that's my recap. Comments, additions, thoughts?