From the video of the man walking on the bridge...I have always thought mid forties. And, sure enough, LE finally came up with a new pic and said it could be someone 18 to 40 and look younger than their age.
Always thought BG was a man who had the day off from work, or got off early in the morning. (Monday, right?)
And, IMO his walk indicated an injured/sore/sciatic left hip. It had the "lead step with the right foot and a follow-up slight drag with the left leg." (I call it step-drag, step-drag, step-drag.)
And, familiar with the area because he was a "deer hunter" at one time.... the "double S bend" of the creek is where a hunter would frequent or stalk because the water is shallower, flows slower and a place where deer can be found drinking water and cross through the slow moving current.
We have only been privy to a short voice clip, yet I feel it was a reply to a question and not a command. Maybe along the line of, "We are looking for our friend Anthony Shots, have you seen him?" And the man replies, "Yeah, down the hill." Once the girls started down the hill, he brandished a weapon, they were unable to flee back across the bridge because he now blocked their ability to run back across the bridge. BG doesn't appear to be a runner/sprinter because of his hip and had to take control quickly. Again IMO, he also had to have a lot of upper body strength if he moved the victims to a less visible area.
Since I am techno-ignorant, would it be possible to access the AnthonyShots real time communications if they had the password to get into that account? Maybe the killer thought he could get away with his crime because this was not his backyard, so to speak, but still an area with which he was familiar.
It's been 5 long years and I know LE wants to get it absolutely correct. I don't want a person to get off because, their defense is, "It's all circumstantial evidence."