Tsarevich Dimitry Ivanovich of Uglich (10/19/1582-5/15/1591), the youngest son of Tsar Ivan IV the Terrible, accidentally killed himself by stabbing himself with a knife during an epileptic fit.
Fr. Francis Dvornik says, “The reports on the death of the real Dmitrij were re-examined by G. Vernadsky (see Bibl.). He has rightly shown that the tsarevich’s death was accidental and that Boris Godunov was unjustly accused of his murder. A complete bibliography on this problem is given in his study published in the Oxford Slav. Papers. On the spread of this legend see also A. A. Rudakov’s study in Ist oriceskie Zapiski, 12 (1941), pp. 154-283″ (The Slavs in European History and Civilization, Rutgers University Press, 1962, 486 n. 1).
George Vernadsky points out that the testimony of the people who were in the courtyard at the time of the tsarevich’s death (“Vasilisa Volokhova, Irina Tuchkova, Maria Samoylova, and the four boys, Dimitry’s playmates”) is to be preferred to the testimony of “witnesses” who were not (Tsaritsa Maria Feodorovna Nagaya and Mikhail Nagoy) — see (The Death of the Tsarevich Dimitry: A Reconsideration of the Case, Oxford Slavonic Papers, Vol. V, 1954, 15-17). The Stledstevennoe Delo, the official investigative proceedings, is a more reliable source than the 17th century Russian chronicles (op. cit., 19).
The Catholic tsar False Dmitriy I was not the real Dmitry, nor was he the renegade monk Grigoriy Otrepyev, but he was not strictly an impostor (Thurston, Herbert. “Impostors.” The Catholic Encyclopedia, vol. 7. New York: Robert Appleton Company, 1910. 9 Sept. 2015 <http://www.newadvent.org/cathen/07698b.htm>); due to his upbringing by the boyars he genuinely believed he was the son of Ivan the Terrible (George Vernadsky, A History of Russia, New Haven: Yale University Press, 1969, 116-117).
The above account renders unworthy of belief the story related by Bishop Nikolaj Velimirović of Ohrid and Žiča (Prologue from Ohrid, June 3), who is commemorated by Orthodox Christians on May 3, that Boris Gudonov murdered Dimitry. If Bishop Nikolaj meant that Dimitry posthumously appeared to a monk informing him that he was murdered by Boris, we must reject this alleged vision as unhistorical. I invite the reader to suggest whether a serious investigation by the Congregation for the Causes of Saints would affirm whether any of the alleged posthumous miracles by Dimitry are what Fr. Louis Monden, S.J. would call “major prodigies” with intrinsic apologetic value which would “by [their] context or circumstances suggest or confirm” an interpretation of doctrine opposed to the teachings of the Catholic Church; cf. my article “On Miracles Outside the Catholic Church,” n. 7.