I don't know why, but reading this made me recall a guy I knew when I was in college... I had a group of male friends, none of whom I ever dated.. but we did flirt a lot, joking around. There might have been crushes going on, but no-one ever acted on any such feelings. Anyway, the little quiet funny guy of the group, who everyone was really fond of and always seemed kind of sweet ended up showing some shocking true colours one night when all the other went out to get drinks and left us alone. He was nice and sweet as usual, but then he suddenly turned VERY nasty. I mean, he said some incredibly cruel and hurtful things, hateful things, like he despised every atom of me. Stuff about how I was a stuck-up tease who liked to lead men on, how I was such a princess and someone ought to teach me a lesson the hard way, etc etc etc. I did NOT know what to do. (eta: And his face!!! It was literally 'a mask of rage'!)) And I genuinely got rather scared of him. When the others got back, I was crying my eyes out. The guy laughed it all off, minimised the whole thing, "I was joking, hey she takes thing way too serious, hey c'monnn I'm sorry!" But not until the others entered that room. I never saw him the same way again, after that, and neither did his friends I think.
Idk why I felt I had to share that, aside from maybe thinking Carmen's killer was somebody she was not at all threatened by, someone she knew, maybe who 'swung by' with some extra food and drinks and all the while he's planned to try to have sex with her. But I think he was already full of rage and a desire to show her what was what, maybe he needed to feel that she'd 'pushed him to it' by accepting his food and drinks and company and then rejecting him (as he maybe knew she would).