We don’t know what Wally’s reason was for creating the crime scene he did, but he does seem to have one and it doesn’t seem like it was done with insidious intent. Dude just killed everyone, tapering with the scene seems tame by comparison. Of course it’s not in character, its not suppose to be in character. He’s had a mental breakdown and is acting irrational. Now not like the mental breakdown all you want, which is completely fair, but you don’t have mental breakdown and act in character. The entire point is he’s not in his right mind. To me it seems that he has deluded himself with some idea that he can fix things, which is not actually that crazy given their world, rather then accept what he did. Cause how could he accept that. I mean Barry couldn’t accept his mom dying and rewrote the Universe.