Q. On question above (if a Cohen physician that unintentionally ended the life of a patient, can continue reciting Birchas Cohanim), does it matter if the patient was not Jewish?
A. Pri Megodim (E”A 128; 51) mentions that it applies even to Gentiles, since Mechilta (Mishpotim) maintains that capital punishment bidei shamaim, or by the hands of heaven, also applies.
However Maamar Mordechai (128: 43) quotes from Perisha, that inasmuch as the pasuk “Your hands are full of blood,” which is the source for this halacha, deals with the Jewish nation, it therefore only applies to them, and not to Gentiles, even if when they keep the Seven Noachide Commandments.
Tzitz Eliezer (14: 60) similarly rules that this restriction does not apply when the patient was a Gentile.
Horav Shlomo Miller’s Shlit’a opinion is similar.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a