Frightening and possible. But weren't they already off the end by this stage? ( 2.30 vs SC pic 2.07) Then this was perhaps followed by " Guys, this is private property so you need to go down the hill."
He could even have also said " I'll show you the way across the creek to short cut back to the trail". What option would they have had really rather than do what the adult is telling them? AJMOO
Yes that could have happened. I think Abby was not off the bridge yet yet due to what looks like a bit of her jacket inside the photo's frame. But even if she had gotten off and was standing by Libby MOO BG closed in on them to threaten and direct them with a handgun,