. >> what was your opinion of brendan dassey? a shy kid, somewhat introverted. >> but once he opened up, the details he revealed would stun investigators. >> what else did he do to her? >> raped her. >> did he tell you that? >> fassbender says dassey described a brutal scene. on that halloween afternoon, his uncle asked him to come over to his trailer. dassey said they each sexually assaulted teresa in avery's bedroom. and avery later shot her in his garage, burning her body in the bonfire. >> it's a game-changer. he told us stuff we weren't really aware of, like teresa was shot in the garage and had died there. >> and after speaking about dassey, fassbender had his team return to the avery property once more. and they found this in his garage, a bullet fragment. >> and that was missed the first time around. >> well, i guess i could say it was missed. but you're talking about a bullet fragment, looks like a piece of dirt probably. >> and it was tested? >> it was tested. >> and do you now believe that teresa was shot in that garag