I think KY and JR headed straight to grandpa's house after leaving the party. That would be the most logical place to go. JR was driving and she may have thought she'll just drop KY off there but then KY has invited JR to the house or something like that. AY told that the car was parked there in the morning, so I think JR definitely was there too at some point. I also think she never left AY's house alive.
If the coworker's story is true and KY had scratches in his face in the morning, someone really resisted something he did that night. Those are typical wounds you get when you're strangling a woman. When the attacker's hands are tied to the neck of the victim will try her best to hurt the attacker in any possible ways with her hands. Women are taught everywhere to claw and scratch an attacker so they leave a visibles mark on the attacker's face that the attacker cannot hide. JR did a good job at that. Good girl!!
I think KY's dark side took over at AY's house when JR was there putting him to bed. If the things a former girlfriend has told is true, it's quite possible KY attacked JR after getting rejected. JR had a boyfriend at that time, so she probably turned down KY's proposals. And KY likely did propose something JR was not likely to accept - even at the party he was reportedly babbling about marrying JR and stuff like that.
Grandpa might not have heard anything, that really depends on how the bedrooms are located and if there's any insulation. Does anyone know if KY's room was in the basement or something?
I'm still wondering if KY did hide the body that night or if he just covered the body with sheets and transported it somewhere later.
