Wilt thou kill me - How it was known that he had killed the Egyptian does not appear. It was probably communicated by the man who was rescued from the hands of the Egyptian, Exodus 2:11-12.

Wilt thou kill me as thou didst the Egyptian yesterday? That is, is it thy will? dost thou design to kill me? or, as in Exodus 2:14 "intendest" thou to kill me? In the Hebrew text it is, "wilt thou kill me, dost thou say?" that is, as Aben Ezra rightly interprets it, dost thou say so "in thine heart?" which is a much better observation than that of Jarchi's;
"from hence we learn, says he, that he slew him by the ineffable name:''
though this is the sense of some of their ancient doctors (c);
""to kill me dost thou say?" it is not said, "dost thou seek?" but "dost thou say?" from whence you may learn, that the ineffable name was made mention of over the Egyptian, and he slew him.''
The word "yesterday" is added by Stephen, but with great truth and propriety, and is in the Septuagint version of Exodus 2:14. The "as" here does not intend the manner of killing, whether by the fist or sword, or by pronouncing the word Jehovah, as Jarchi thinks, but killing itself, by whatsoever way; and the words were very spitefully said, on purpose to publish the thing, and to expose Moses to danger of life, as it did.
(c) Shemot Rabba, ib.

Wilt thou kill me, as thou didst the Egyptian yesterday?--Moses had thought the deed unseen (Exodus 2:12), but it now appeared he was mistaken.