The policeman would likely show up on the scene about an hour after Eliza's network post and clear everyone out, plus wrap the area in crime scene tape... But they can't watch everyone necessarily, so it would be easy enough for someone to just slip out of sight and loop back around to the body. From then on out, he'll assume he has secured the area and basically just patrol along the edge of the woods, watching for any sign of someone trying to sneak in. But he's had a long day and his senses aren't the sharpest, so it's possible for him to give him a wide berth and come at the scene from the side (or even the opposite riverbank) and make it to the scene unimpeded.

If the pictures are known to have been taken, they'll be in trouble. However, surveillance in the woods is at a bare minimum and as long as the pictures aren't mentioned or waved around within city limits, it should be fine!