This is the spookiest picture imo.
Some thoughts:
It was less than 6 hours after they embarked on the trail when they tried dialing the emergency number. It's clear they were already lost at this point; as an /out/ist you should know how easy it is to get lost in unknown terrain, especially considering that it was dense jungle and two clueless backpacking euro girls.
By the looks of where some of the girls' stuff was found (particularly the jeans)
>>1326482they seemed to have reached a river at some point and continued following it, Rio Changuinola I think. They tried following it downhill, thinking they would eventually reach the shore and civilization that way. This is where one of them got injured. Not wanting to leave the injured person alone, the other girl stayed with her until she too was too weak to continue along the river. It's also a possibility that it simply wasn't possible to follow the flow of the river at some point due to a steep cliff or ravine or something so they had to stay where they are.
The weird flash pictures taken at night a week after were taken by one of the girls due to panic or paranoia; animals at night in a jungle must be horrifyingly loud. The other was probably dead at this point. It's also possible the surviving girl took the pictures thinking they might work as a sort of rescue signal (cute idea). Eventually she succumbed to hunger herself. The corpses ended up in the river some way; it's possible the girl that survived longer pushed the other girl's corpse into the river when she started rotting.
The homicide/local town rapist idea is /x/ territory imo. I don't see foul play.