See Rashi (Shemos 2:12) "וירא כי אין איש" - שאין איש עתיד לצאת ממנו שיתגייר : Before Moshe Killed the Egyptian he looked [into the future] and saw that no person would descend from the Egyptian who would convert to Judaism. Obviously, in order to look into the future, Moshe had to transcend to where the dimension of time does not exist(למעלה מן הזמן). In the plane of למעלה מן הזמן everything of the past, the present, and the future exist simultaneously. This being so, the "future" which Moshe saw also included the act of his killing the Egyptian, (which he eventually did). Thus, it would be obvious that he would see that no person would descend from the [killed] Egyptian who would convert to Judaism, so what was he looking for?