I agree it’s weird. I’ve begun to question whether these witnesses actually saw BG or if they did, they saw him before he accosted the girls but not after.
My current theory...my previous 3,567 theories should now be considered secondary
...is that BG is very familiar with the trails and the area and visits with someone there frequently. Perhaps works occasionally for farms around there. He was visiting or housesitting at one of the rural houses within a couple miles of the trails and while driving spotted the girls on the way to the trails and followed them. Saw them pull into the trailhead parking drove past and parked himself at the CPS building deciding on the spur of the moment to attack them. He had a gun and knife in the car and took those with him. He wasn’t sure an opportunity would arise. It did. He trapped the girls at the end of the bridge. I think his intent was to take the girls to either the little deer shed/shack on the south side of the creek or to a barn or out building at a nearby farm on the north side. If he had evil intent to attack them I would think someplace a little warmer would have been his plan. I can’t imagine sloshing through a freezing cold creek was his plan unless he was trying to get them somewhere inside. Anyway...the girls bolted and tried to escape by running across the creek. This sent the killer into a rage and when he finally caught Abby he killed her with his knife quickly. Libby came to her defense and the killer turned on her and a fight ensued eventually battering and injuring her much worse and eventually killing her too. By now he is so angry at them for spoiling his plans he moves them to where they are found and poses them or defiles them in some way that shocks LE when they are found. The killer is startled out of his killing trance by Libby’s phone ringing. He leaves by heading up the creek away from the bridge thinking he cannot head to his car or he will be seen. He follows the creek for awhile sometimes wading in to rinse blood off his clothes. Then leaves the creek to walk across fields or the tree line to whatever house he’s staying at. It is during this trek I think the person who helped with the first sketch saw him and decided it was “something that needed reporting”. After showering, washing or maybe burying his clothes, gun and knife. He calls someone he knows and tells them his car broke down and is parked at the CPS building. They help him retrieve his car. He stays in town a few days so it doesn’t look suspicious. A few days later he leaves town. Never has been back.
All just my thoughts and opinions...until I come up with another theory.
Feel free to point out the flaws!