I'm curious who she was texting before she allegedly texted her boyfriend with the abduction text. That she was supposedly not sexually abused makes me wonder a couple of things.
First, why? What would be the incentive for a stranger to kill a young woman? Is this someone she knew? Were they in contact with her before her death and did they know she would be on that trail?
Or was the motive of a sexual nature by a stranger but someone unexpected came up on the trail (either the van, or the motorcycle) and foiled the plan?
And possibly, as others have mentioned, this was a hit and run. Which I doubt for some reason, but it's possible based on her injuries.
Regardless, I think this person is a local or very familiar with the trail, knowing that it's not a busy trail and that they would not be easily caught.