Initially, Milarepa had studied to be a sorcerer practicing black magic.
His uncle and aunt swindled him out of his inheritance, but he got vengeance by conjuring a hailstorm that killed people and destroyed their homes and crops, but left the uncle and aunt alive to feel the impact of this vengeance.
Later he regretted his actions of black magic, and so he sought a spiritual teacher to him find the right spiritual path.