Guess is the feds will claim the crime occurred on a national trail, akin to national park. They will rely on 18USC7 (special maritime AND territorial jurisdiction of the United States).
However, if they defense lawyer has balls (highly UNlikely), he will challenge the jurisdiction because the feds ONLY have jurisdiction if (a) the state legislature consents and (b) it is for the purpose of the federal government's "the erection of a fort, magazine, arsenal, dockyard, or other needful building."
They will claim there are "needful buildings" on a national park trail, but if the crime did not occur in such building, the feds have ZERO jurisdiction.
Fed lawyers just doing what they've been getting away with for decades, and defense lawyers having NO BALLS to call them out on it.