FWIW, from this link:
Though all that was told was not true, the incident exercised as deep an influence then, - and has ever since in its various forms as if it were. But Jane McCrea was not killed by the Indians, though she was their captive...
Read on at the link for the rest. It's a long paragraph :)
Interesting link.
However, we may never know the real details of the event beyond the fact that she was scalped and a Wyandotte Panther was probably the culprit and she was engaged to a British soldier and the event was the cause of American outrage.
Despite the highminded exhortations of the British, the indians had a long tradition of taking these trophies in combat and their standards of conducting warfare were closer to those of the British settlers of the 1600's than to the chessboard type "civilized" warfare conducted in the 1700's.
Burgoyne was certainly aware of the behaivour of the indians in the employ of the French during the French and Indian Wars as well as that of the British indian allies during the same conflict.
But the simple fact was he could not dispense with their services as they were unsurpassed in the kind of scouting and ambush irregular warfaew conducted in the wilderness.
A visit to the musuem at Ticonderoga will provide one with some samples of scalps taken by the indians in the French and Indian wars.