Unfortunately, the perp(s) seems to have carefully planned this in order to evade police. I think, in particular, they didn't waste any energy trying to create a false scenario to mislead police, such as a robbery gone wrong, or a missing person. Darkness, outdoors, isolated victim, element of surprise, keep the weapon and vehicle out of hands of police. Still, what they can't conceal, IMO, is the obvious foreknowledge that she would be there, alone, at that time and place. And there must be a rational motive to plan and carry it out it so carefully.
ETA: IMO, police aren't going to inform the public about any suspects, as they would likely be watching them carefully.