The north side of the bridge means its on the north side of the creek. The bridge itself does not run straight north / south. It runs at an angle.
Based on the what can be seen in the photos (namely the planks off to the sides of the bridge, one having additional wood hanging off of it & shadows) I can say that both photos were almost certainly taken by Liberty from nearly the exact same spot but she turned 180 degrees.
Based on Gray Hughes' work we can be fairly certain the suspect's photo was taken from the south side.
The green circles indicate where the camera taking the photo was positioned, green lines showing field of view & direction.
The bodies were found on the north side of the creek. South east of the cemetery.
Based on this information: If the suspect seen in the photo was involved he either had to force, lure or follow the girls across that bridge and to then to the east *or* they had to go through the creek itself.
It also seems possible to me that the girls crossed the bridge on their own, were exploring the woods south of the cemetery and someone over there attacked them. Possibly the guy in the photo following them as they explored the woods. Maybe someone else, maybe him & an accomplice.