Graphic warning:
A thought came to me about the "not finishing" part of the rape - the detail about LE not finding semen on her.
What if Karina kicked him in the groin really, really hard?
That would not only hurt, but anger him. Looking at her legs on the video, she was strong! LE has said, IIRC, that the attack escalated because she fought so hard. Perhaps she fought so hard in one particular area, and that escalated the violence dramatically. And maybe that's why he threw her shoe? Maybe he grabbed her foot that kicked him, tore off her shoe, and threw it?
She was brutally raped without semen. Perhaps he raped her with something else - his fist or a stick? Sorry for being graphic.
If this kick to the groin happened, surely his pain was felt for awhile? I'm female so I don't know how long an injury like that would hurt, but I would think he might be walking a little funny for awhile...in addition to being ANGRY after this crime. I assume some rapists feel elated, relieved, or remorseful....but I envision this guy very angry if he was injured to the point of not being able to function in the rape.
Surely someone who knows him would've noticed not only scratches but perhaps him hunching a bit in pain, scowling, angry. I have a feeling that anger would stick around for awhile - longer than the scratches on his skin. Perhaps the anger flares up whenever the story hits the news again, like yesterday with the video release.
This worries me very much because it's possible he'll want another victim to prove he can do it.
Total hunch, speculation, thinking aloud.
JMOpinion