A few thoughts. All very much MOO.
Agree with all of you that stated this press conference was calculated and targeted directly at the killer.
Carter looked genuinely agitated and emotional. Could be a ruse but it seemed genuine. I believe they have uncovered new information that is making them look at someone they had previously dismissed or at least moved to the bottom of the pile. This person is either a respected person associated with the community or close to one of the families or law enforcement. To me it was almost as if Carter knew the suspected killer personally and was still in shock and disbelief. Could also explain the supposed angry/tearful reaction from close family.
As to why this new old sketch wasn’t released earlier, two thoughts 1) maybe the person had a reason to be at the trail and had a valid alibi that said he was with them during the important window of events, 2) maybe they’re just learning that BG was wearing a disguise, bulky clothes, hat to hide distinct hair, and most importantly facial hair. I don’t think a facial disguise is highly likely, just trying to make sense of it all.
One thing that stood out to me was referring to a change in direction/tactic (sorry, don’t have exact quote at the moment) and how the killer wouldn’t be expecting this new tactic. Is the new tactic dusting off an old sketch that was originally ruled out? Are they expecting a family member who provided an alibi to feel guilt and turn them in (or at least admit they weren’t with them during that time)? Edited to add: maybe the anger displayed at the press conference wasn’t so much with the killer (stick with me) but at the person who has been covering for the killer. What if that person is respected or close to family and all this time they were covering because they were in denial. So many new questions.