Commentary on the story:
http://www.chabad.org/parshah/in-depth/default_cdo/aid/1149/jewish/Summary.htmFlight From EgyptAnd it came to pass in those days, when Moses was grown, that he went out to his brothers, and looked on their suffering; and he saw an Egyptian smiting a Hebrew, one of his brothers.
He looked this way and that, and when he saw that there was no man, he slew the Egyptian, and hid him in the sand.
But not only Egyptians were doing the smiting. The next day, Moses encounters two Jews fighting. "Why will you smite your fellow?" he demands of the attacker.
"Who made you prince and a judge over us?" comes the reply. "Do you say to kill me, as you killed the Egyptian?"
And Moses feared, and said: "Indeed, the thing is known."
Moses' fear materializes: word reaches Pharaoh, and Moses is sentenced to death. Moses flees to the land of Midian.
He went out to his brothers, and looked on their suffering (2:11)He saw great burdens put upon small people and light burdens upon big people, and a man's burden upon a woman and a woman's burden upon a man, and the burden which an old man could carry on a youth, and of a youth on an old man. So he left his suite and rearranged their burdens, pretending all the time to be helping Pharaoh. G-d then said to him: "You have put aside your affairs and have gone to share the sorrow of Israel, behaving to them like a brother; I too, will leave those on high and below and speak only with you."
Moses saw that they had no rest, so he went to Pharaoh and said: "If one has a slave and he does not give him rest one day in the week, the slave dies." Said Pharaoh: "Go and do with them as you say." Thereupon Moses ordained for them the Sabbath day for rest.
(Midrash Rabbah)
And he looked this way and that, and when he saw that there was no man (2:12)He saw that there was no hope that any righteous person would arise from him or his offspring until the end of generations.
(Midrash Rabbah)
And he slew the Egyptian (2:12)How did he slay him? Rabbi Abyatar said: With his fist. Others say that he took a clay shovel and cracked his skull. The Rabbis say that he pronounced G-d's name against him and thus slew him; thus [the Hebrew he saw fighting the next day] said to him, "Do you say to kill me?"
Two men of the Hebrews fighting (2:13)These were Datan and Aviram (who were yet to cause much trouble for Moses - see Exodus 16:20 and Numbers 16).
(Rashi)
And he said to the wicked one: "Why would you smite your fellow?" (2:13)Said Resh Lakish: He who lifts his hand against his fellow, even if he did not smite him, is called wicked; as it is written: "And he said to the wicked one: Why would you smite your fellow?" It does not say, "Why did you smite," but, "Why would you smite," indicating that though he had not smitten him yet, he was termed a "wicked one."
(Talmud, Sanhedrin 58b)
And Moses feared, and said: "Indeed, the thing is known" (2:14)Moses was meditating in his heart: "In what have Israel sinned, that they should be enslaved more than all the nations?" When he heard their words, he said: "Tale-bearing is rife among them, and how can they be ripe for salvation?" Thus he proclaimed, "Indeed the thing is known"--now I know the cause of their bondage.