Why did Moses have to flee after killing the Egyptian?

Moses fled because Pharaoh sought to slay him after learning that Moses, the second man of Egypt, had killed an Egyptian. Murder was against the law, and Pharaoh intended capital punishment. So Moses escaped from Pharaoh's face and dwelt in the land of Midian, east toward the Sinai Peninsula.

Les explains that after Moses killed the Egyptian, he had to flee because murder was just as much against the law then as it is now, only the results were worse. In Exodus 2:15, when Pharaoh heard that Moses, the second man of Egypt, had killed an Egyptian, Pharaoh sought to slay Moses, carrying out capital punishment. So Moses fled from Pharaoh's face and dwelt in the land of Midian, east toward the Sinai Peninsula, and sat down by a well.

Exodus 2:15

Now when Pharaoh heard this thing, he sought to slay Moses. But Moses fled from the face of Pharaoh, and dwelt in the land of Midian: and he sat down by a well.

What did Pharaoh do when he heard Moses had killed an Egyptian?

Pharaoh sought to slay Moses, carrying out capital punishment, after hearing that Moses, Egypt’s second man, had killed an Egyptian. Moses fled from Pharaoh’s presence and dwelt in the land of Midian, east in the Sinai Peninsula area, and sat down by a well.