[He turned to Beatrice.] If you are the culprit, this is a distance killing. While you 'know' them, you do not have a true connection. In that way, to kill all these people, then this crime is a contradiction.

[He held up two fingers.] Because this would be the killing of a serial killer style in which case there are only two killing style. The chaotic one and the orderly one. [Gestures to the shudder.] That symbol. [Then the bodies.] The fact the bodies were damaged after death and all in this one place. Those actions say this is the work of the killer who has ritual. Who has to make everything 'perfect' and 'uniformed.'

But there's an inconsistency. With Shannon and Krauss. The faces were damaged after death. There is no reason both their faces not to be completely destroyed like the other four. Because of the obsession that type of killer would have, there's no way they could leave half a face on anyone, let alone two. And that proves that no matter who the killer is, they knew these people, and the people knew them, and that there was more personal feelings here than to follow a ritual.

Then things make more sense. [Walks over to one of the bodies, gesturing to the face.] They did this post mortem. Why? Simple. Because they hated these people. They hated them so much they wanted to erase their very existence and destroyed their faces.

Shannon and Krauss were spared because even if the person hated them enough to kill them, they didn't hate them enough to completely erase their existence. They might not have even hated them enough to bash in both their faces, but they thought if they didn't, then it'd be suspicious. However, they couldn't manage enough anger or fear they would need to actually erase their whole face and they left that clue anyway.