The Killer in Me/Playing With

In a twist, one of the main characters turns out to be the killer.
 * Straight: After pursuing the killer throughout the entire story, it turns out that Bob committed all the murders.
 * Exaggerated: After pursuing the killer throughout the entire story, it turns out that Bob, along with every other character not a victim committed the murders.
 * Downplayed: Bob is only partly responsible for the murders, while the actual kills were committed by someone else.
 * Justified:
 * Bob was trying to allay suspicion by leading the investigation himself.
 * Bob is psychologically disturbed and blacked out everything (see Type B).
 * Inverted: It turns out that the killer actually didn't commit the murders and is really the hero.
 * Subverted: Bob is revealed to have been the killer, but then is exonerated.
 * Double Subverted: The exonerating evidence was planted by Bob.
 * Parodied: The hulking 6' 9'' killer turns out to have been a petite young woman who looks nothing like him.
 * Deconstructed: Having blacked out everything, Bob is so in despair at the revelation that he hangs himself.
 * Reconstructed: Therefore taking his secret to the grave with him.
 * Enforced: Not having pinned down the identity of the killer in advance, the writer thinks it would be a great twist to have him turn out to have been the main character all along.
 * Lampshaded: "So Bob is the real killer! ...I didn’t see that one coming."
 * Invoked: Bob decides to commit murder because nobody would suspect him, being the lead murder investigator.
 * Defied: Because Everyone Is a Suspect, Bob's first priority is to prove his innocence in the recent string of murders.
 * Discussed: "It’s always the one you least suspect... least of all the one leading the investigation."
 * Conversed: "In this new mystery novel it turns out that Bob is the killer."
 * Played for Laughs: Two of the leading inspectors make a bet on whether Bob is the killer.
 * Played for Drama:
 * Alice is traumatized at the revelation that her best friend was the murderer.
 * Having blacked out everything, Bob is in despair at the revelation.