The witness of sacred history
In the account of Abel's murder by his brother Cain, Scripture reveals the presence of anger and envy in man, consequences of original sin, from the beginning of human history. Man has become the enemy of his fellow man. God declares the wickedness of this fratricide: "What have you done? the voice of your brother's blood is crying to me from the ground. And now you are cursed from the ground, which has opened its mouth to receive your brother's blood from your hand."
Source: Catechism of the Catholic Church (Vatican.va)