I dont think we can have it both ways.... either they have more video "the stuff of nightmares" or they are bluffing.
1. if theres more video then why can they not determine if there were more than one perp. How do they not have more audio? Either they are watching the video or they are hearing audio... either way they should have more information the he BG and if there are more suspects... real simple was there ever anyone else on the video.
2. they are bluffing to make the perp think they caught the crime on video in order to get a full confession of what happened to the girls because they are not completely clear. Autopsies do not tell the whole story, even with a COD what the events were leading up to the death can still be a mystery.
These are just my opinions