After hearing part of the press conference (problems with sound on laptop), I am so angry I can't even think right now. I feel so bad for her parents and loved ones.
My first thought was that the "words" spoken were carefully crafted. It does appear that they do know much, much more than they can put out there right now. I'm thinking that someone in jail is spilling their guts out to try and make a deal for themselves and the FBI need to confirm his story. It's obvious to me that at least part of the story has been corroborated because surely Brittanee's parents would not be told that she was brutally murdered if it was just a jailhouse story. I've always been suspicious of the brothers, who IIRC lived in a very tight knit community, family goes back for decades in the area. These people would not, IMO, rat the murderers out, so it must be someone outside of the brother's family who is trying to make a deal for himself.
I pray that LE is just trying to tie up loose ends before they arrest the monsters responsible.