Jon allegedly abused his fellow student along with other fraternity members while studying at the University of Texas in Austin, court records show.
Members of the Sigma Nu frat house are said to have pulled a new recruit out of his bed in the dead of night, subjecting him to a two-hour ordeal of physical abuse as part of a 'hazing' ritual for new members.
The star, who plays Don Draper in 'Mad Men', supposedly set fire to the student's underpants and refused to let him put out the flames, and later hooked the claw-end of a hammer to the man's genitals and dragged him around a room with it.
The next morning, the victim was found by his mother "hiding in a closet at his apartment, his buttocks and legs black with bruises".
Despite begging his mother not to call the police because he feared for his life, she rang 911 and landed three of Jon Hamm's friends in prison for thirty days. Charges against the 'Mad Men' star were eventually dropped.
A friend said: "The hazing incident was an isolated incident in Jon’s life. Since then, he’s been strong enough to take steps to make himself a better person."