8 Then Cain said to his brother Abel, “Let's go out in the fields.” When they were out in the fields, Cain turned on his brother and killed him.
10 Then the Lord said, “Why have you done this terrible thing? Your brother's blood is crying out to me from the ground, like a voice calling for revenge. (Genesis 4:8, 10 GNT)
As we know Cain was exiled for 'this terrible thing' but the strange thing is why God just punished Cain and not end his life?