Definitely don't think she was alive for long after she left the Academy. If she indeed died in his apartment, he might well have left her there, gotten her car as far away from his place as he comfortably could as quickly as possible, then walked home and waited for middle of the night to move her body to CB.
Those "chards" of glass inside the car become interestinger and interestinger. Now where did they come from to be inside her car if he didn't drive it to Pitcher Canyon AFTER first heading to CB?
Unless they turn out to somehow be completely unrelated to this case and were there before this all went down.
Short time frame indeed if CB was not the crime scene and perp had to take the time to move a body to a vehicle in broad daylight without being seen. Then move it down to the river. All the way back up to Pitcher to leave the car, and be seen possibly as early as 4:30pm walking back to town. Even 5:30 is making pretty decent time, and that doesn't include however long he spent attempting to cut off an arm with a cheap knife.
And used duct tape for something. To hold whatever he may have had her wrapped in to either disguise it was a body if seen and/or help move her body down that hill to the river? Perhaps a piece of it came loose on the "drag trail" and he failed to notice he'd left vital evidence behind.
Wonder if anybody saw him moving an old rolled up carpet out of his place? (OK, too much TV!)
ALL speculation and MOO only at this point!