You are hung up on this whole idea of "new". Nothing "new" has to happen for case or decision to be used as a precedent in future cases.
It simply means precedent "requires courts to apply the
law in the same manner to cases with the same facts."
But since you seem to want "new", how many previous cases have there been of a 17 y.o. traveling out of his home state, uninvited, to a neighboring state in order to play cop during a riot, and shooting and killing two unarmed men, and shooting an maiming an armed man?
Seems to be a rather unique situation to me.
Do you know of any very similar ones?