It's cool to see the conversation livening up again here. I'm going to reread the first topic. Hit a busy patch at home but following along.
Re the long post on NPD qualities, I do think they fit SC extremely well. Also there is nothing that does not fit. At first he was relatively cooperative, but as soon as he started getting negative press, his personality got very sulky, withholding, insulting, accusatory, and wounded in affect. Then there was a Facebook page exposing his secret ID and commenting on his posts criticly. Most people would not like that, but for NPD it was not tolerable. It is notable that this guy (the family and the state believe) murdered and dismembered his girlfriend and unborn child, and yet his whole concern becomes about the PR he is getting as if he doesn't deserve the flack. He really shows no signs of remorse to this day.
After the forensics comes back, and Charli is declared deceased, he starts to unravel even more, issues ultimatums about his stuff to the family, engages KS in a conversation where he threatens her that she will see the monster, then sends a terrorizing snap chat pic to a teenage sister and maybe others. He then recklessly disregards a bench warrant and finally goes into the station wearing an illegal knife. Wow.
You can see the disproportionate value he puts on his image, and how losing his fan club shakes him up. Then he makes that switch to -- fine, I'll just embrace the notoriety and show my evil side, because, I think, he hates the comments dismissing him as nothing, insignificant. He needs to show them he is something. He is evil, a monster, they cannot ignore him.
I don't see this personality as ever being likely to show compassion for the family by revealing the location. The only way he would is if he believes the knowledge will hurt them more. He will never want to help heal them.
All that said -- I think his comment about Charli having "a mouth on her" that could piss people off, which many here have discussed -- says it all about why he had to kill her, silence her. As a narcissist who had been relating to Charli for five years or so, he probably had a mental file folder of every remark ever said that denigrated something about his wonderful self's behavior. This type cannot abide criticism. It sounds like she was fairly deferential to him when they lived together, and served him, catered to him, and so forth, but now she was making her own decisions about a child without regard to how he felt or what he wanted (in his mind). Unacceptable.