Who didn't know the killer? - Spoiler (?)

If you give a crap and haven't watched the movie do not read.

Who didn't know who the killer was after the first 20 minutes?
Not because they gave away too much info but because it was 100% A-Typical Movie Rhetoric.
1st - She's the only person that he didn't suspect... and he suspected anyone in a 10ft radius.
2nd - He said not once, but twice, "Don't beat yourself up...", a clear foreshadowing - she beat herself up (literally).

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The World is My Oyster...
Completely Shucked!
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