So I don't get it...

I liked the film in parts but I didn't really get what really happened, this has probably been asked before but I only just seen it. Who actually killed all those people because the obvious choice would be Sharon, but it made sense when she said it was him at the end, but also that the police was a crook, because all those people backed that story up that the police guy was a crook...i thought it should of been clearer. And even if it was sharon who did theres no way she can get away with it no matter how much dosh she got, because for one their were witnesses that would of seen her with that girl going into the bathroom, plus there are cameras in the hallways of those places AND in the clubs so that would of been on tape! Someone would of also seen her go in with that sex maniac man because theres people all over, PLUS there would be traces of her all over the places, including fingerprints of hers on that red clock tower, traces of her hair and stuff on the bed and that...no way could she skim through that...so maybe he did kill all those people just he had the law on his side because they were after catchin her, so thats why they didnt prosecute him they didnt wanna believe it...until they saw him shoot the cop...so I dont know I just hate unresolved things like that lol but I liked the gameplaying aspects I thought she was a very clever sneaky biatch!