I'm confused too, I get that the main events of 3 and 4 were actually running parrallel but I don't get how the police guy got in on it with Amanda and Jigsaw, unless that actually wasn't explained. At first I understood it to be that because he survived the trap and then discovered the tape he felt compelled to take over but then tht doesn't fit in with the timeline at all, so what am I actually supposed to know at the end of this film?