Sorry in advance if this theory has already been posted - the thread is too long for me to read completely. Just wanted to say that after watching the presser, my theory is that BG has been inquiring heavily about progress on the case both in person and anonymously online and he accidentally included an unpublished fact, which caught the attention of the police, who started monitoring him. (I wonder if it was something about how the girls' bodies were left, because the police specifically say the girls are not how you left them). This explains how the police seem to know a lot about BG without knowing his exact identity. I think the police dropped clues to let BG know they're monitoring him (the Shack, the fact that he has a family and that someone has noticed he's acting differently). I'm sure they'll be able to connect the online identity with BG in time, but it'll go faster if the person/people he was talking online with recognize the details and go to the police, or if BG cracks under pressure after realizing he's being monitored and someone reports his unusual behavior.