Reposting in case anyone wants to discuss the combination of knowing that the stills came from Liberty's phone and that they were directed downhill.
Topo on 10' contours.
black arrows point up slopes
The audio has me circling back to roughly my original theory that he intercepted them on the bridge or just coming off of it. Now, KNOWING that the video was from Libby's phone, it appears that he took control of them on the bridge. He may have walked past them since it appears that he he is walking to the South, the same direction of the instagram of Abby and heading in the opposite direction from the side of the creek where the girls were found. I think he could have walked a few feet past them, turned and then directed them back the way he had come from to the North side of the creek. The video is also crucial because it implies that he likely took them to the same side he approached from. I think this is important because he I feel he probably had a reason to go to that side- he knew that side had less houses and that the terrain would give them the ability to hide if need be. He also directed them right off the end of the bridge and not left which would lead me to believe that he was aware of the trail that paralleled the main trail (the trail to the right that the witness said she didn't take) and avoided that side because of the possibility of being interrupted. He took them to the most isolated place available and this indicates to me that he was at least somewhat familiar with the area.
My theory is that he parked in the trees to the rear of the cemetery and made the walk to the bridge. He could have waited in the woods East of the bridge and watched them get out onto the bridge so they would have nowhere to escape. I feel like he could have walked past them pretending to just be someone else on the trail and then ordered them back as soon as he got south of their position. He walked them East and then exited the area via a vehicle at the cemetery and would not have had to go back to the trail anymore. The questions I have here revolve around whether he was seen by others at the park that day. It wouldn't be necessary for him to be on the trails in this scenario risking unnecessary contact.
The drifter angle, which it seems LE is leaning away from makes this all much harder to piece together because it allows for so much more random activity because of the lack of vehicle or means of travel to return to.
The combo of knowing that the stills came from her phone shows that there was definitely an encounter on the bridge and it eliminates the possibility that they were already at the creek bank and sneaked upon. This would mean that he was directing them and that indicates he had a weapon sufficient to control the both of them which leads me to believe a gun. This means he came prepared.