Great question. It’s entirely possible he acted alone and I get why many firmly believe so. My theory is that others were involved digitally, if not physically. If physically involved at the crime scene, others may have entered via the cemetery or another path that didn’t cross with any witnesses. I have toyed with the idea that the girls left the area and got in a car or walked elsewhere and met someone or a group of someones, then returned to the creek bed, but LE is adamant that they were deceased by 3:30. So, that theory doesn’t work.
jmo
My working theory is one of the girls tipped him off they were going to be there.
He is seen walking at pace towards the bridge and he doesn’t get there much before the girls.
I also think this would explain why Libby was quickly alarmed when he started to cross the bridge.
We know unfortunately Abby had been communicating with grown men thinking they teenage boys.
I am likely wrong but I just get the feeling he knew they were going there.
Mooo