The unidentified junior was then allegedly subjected to two hours of brutal physical attacks as part of his fiery baptism into the fraternity.
The alleged victim told police that Hamm and other members hit him with a paddle 30 times and then lifted the pledge off the floor by his underwear, "pulling it back and forth in a sawing motion", causing "great pain".
The pledged then claimed that Hamm led him to a basement "Pit" where he slammed the junior's face into the ground while he was doing push-ups and then allegedly stood on his spine with his full weight.
Shockingly, after this, Hamm is then supposed to have set fire to the pledge's pants and refused to let him pat the flames down, but instead made him blow them out.
At the end of the vicious hazing ritual, the pledge was taken to a part of the frat house called the "Party Room" where Hamm "hooked the claw of a hammer underneath his genitals and led him by the hammer around the room".
Allegedly not content with this, Hamm then went onto to break into another potential pledge's room that night and subjected him to a similar torturous initiation.
However, the morning after, the mother of the first pledge was called to his room to find him "hiding in a closet at his apartment, his buttocks and legs black with brusises."
Despit pleading with his mother not to go public, saying "They'll come kill me!", she reported the incident to the police.
Eight warrants were issued for Hamm and seven other frat members, which was shut down for a time after the alleged incident.
Three members of Sigma Nu were sentenced to 30 days in prison for the hazing ritual and Hamm was eventually hit with hazing and assault charges in 1991.
In the wake of the hazing incident, the Sigma Nu fraternity was shut down in 1990 after the pledge's mother made her son's alleged assault public by going to the police.
In 1990, the AP reported that Sigma NU would close and that seven students were being punished after pledges were "physically and psychologically attacked".
The-then national president of Sigma Nu, James Cherry, said that he was revoking the charter of its UT-Austin, saying, "Basically, we're out of business on this campus".
"But our fraternity was founded in opposition to hazing in 1869 and we will not tolerate any form of hazing today."
A warrant was issued for Hamm's arrest in 1992 but the actor reached a plea deal with authorities in 1995 and the charges were dismissed.
He returned home to live with his family in Missouri and the actor - who recently emerged from a 30-day stint in a rehab facility - began his acting career.
A friend told Star that although shocking, "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."
Recently, the Mad Men star has admitted that playing the complex role of Don Draper has taken its toll.
In an interview he gave just weeks before he checked himself into rehab last month for 30 days, Hamm opened up about the effect that playing Madison Avenue ad man Don Draper had on his psyche.
The 44-year-old star told Variety: "Playing this guy does not come without its own difficulties, it's not fun to live in this guy's headspace year after year."
He added: "People ask, 'What's the difference between you and Don?' Look, I drink, I get drunk. I'm not immune to that,
"And (creator) Matt (Weiner) will tell you, the darkness in Don has not abated, it's gotten worse year after year. It's relentless. And it can be hard on you as a person. I love coming to work; I love the people I work with. But it's been rough."
As he reflected on being offered similar roles and being typecast as the dark, brooding, alcoholic womanizing character, Jon revealed he wants to distance himself from that persona.
- Daily Mail
