The model of the Turk Mustapha Ali is singled out for particular mention by Mayeur de Saint-Paul in his well-informed account of Curtius's salon de cire in the Palais-Royal in 1788:
I was struck by the head of a certain Turk, called Mustapha, who - according to the guide who for two further sous explained what you had not understand for the first two - massacred those who amused themselves setting fire to his beard in the Auxerre coach. This head had great character and expressed fury, just as that of Tarare expressed cowardice. However I could not prevent myself from making a joke which made my companions laugh: I asked how it had been possible to reproduce the lower half of the Turk's head, since his chin had been shattered by a pistol shot in the course of his arrest. Curtius signalled to me to keep quiet, which I did, since I did not want to do him harm.
François-Marie Mayeur de Saint-Paul, Tableau du nouveau Palais-Royal (1788), p.97-8
I was curious to find out more about this Turkish fury. Here he is in a coloured engraving in the Bibliothèque nationale, purportedly "drawn from life by a passenger":
It is worth noting that the Auxerre coach in which the incident took place was not a stagecoach but the famous "coche d'eau" which ran a regular passenger service along the Seine. According to the historian Annie Delaitre-Rélug, there was enough space on board for passengers to stretch their legs, making for "a promiscuity which was not to the taste of delicate travellers".(http://adelaitre.pagesperso-orange.fr/CochesDiligences.htm)
This blog retraces the coach's route:
An account in English was published in several different 19th-century compilations, though this seems only to embroider the information already available from the engraving:
REMARKABLE ANECDOTE OF ALI MUSTAPHA, THE OUTRAGEOUS TURK.
Ali Mustapha, who was born at Candie, in the year 1734, was endued with a most violent and vindictive disposition. This Turk was continually upon excursions, and as he preferred the most economical way, his travelling was always humble. Having entered a barge on the Seine, with his interpreter, the day being exceeding sultry, he fell fast asleep. Three soldiers, who were likewise on board, anxious to have some sport with the Turk, but totally unacquainted with his disposition, took some strips of paper, which they lighted with the candle, and burned his beard almost close to the skin. The interpreter, apprehensive of some ill consequences, endeavoured to dissuade them from their ill-timed mirth; he expatiated much upon the warmth of his master's temper, but no remonstrance availed; they were determined upon fun, and dearly paid for it: the flame touching his chin, awoke the Turk, who, upon discovering the joke, seized a hatchet that was unfortunately lying in his way, and dealt such violent blows promiscuously about, that the innocent as well as the offending, suffered.
His beard now burnt, what vengeance the Turk hurl'd
On all around. He would have killed the world!
During this unequal conflict the people endeavoured to run away, but the impetuous Mustapha followed. His interpreter, for whom he often professed a regard, was first of all attacked, being now esteemed the greatest offender for suffering so great an injury to be offered to him. A nurse and her infant were murdered, likewise the three soldiers whose mirth had incurred this most extraordinary disaster. Some few made their escape by leaping out of the barge; but the accident was so instantaneous, there was no time to think of escaping. One man, who had a sword, endeavoured in vain to defend himself, but it was impossible to parry off the strokes of so dangerous a weapon, guided with such impetuosity. There being now no method to calm his ruffled temper, one of the persons who had a pistol in his pocket, properly loaded, fired at him: The Turk fell, and was secured.
Happy, indeed, there was a pistol near
To stop his wild, impetuous career.
He died three days after this at Sens, in consequence of the wounds he received from the pistol, Sept. 6,1787, aged 53.
The Wonders of the Universe, or Curiosities of Nature and Art, Exeter: J. &. B. Williams, 1836
The caption reads:
Gravure populaire sur bois, coloriée, ou canard, accompagnant une complainte en douze couplets, au sujet de meurtres commis par un Turc, Ali Moustapha, dans le coche d'Auxerre. (Communiqué par M. le baron Pichon.)
Fortunately, the BN has a second variant engraving which includes a somewhat more plausible account of what happened:
There is still no clue as to what on earth Mustapha Ali was doing in France in the first place - sadly, the details are probably lost to history!