Bill Montag, the father of The Hills star Heidi Montag, was arrested in Aspen, Colorado Thursday for allegedly sexually assaulting and incest with a young girl over a period of years.

The alleged abuse began when the girl was 13 and continued until she turned 17, according to the complaint obtained by TMZ. It began in 1993, with the last incident taking place in 1998.

The documents go into graphic detail about the abuse, noted that he would give her “back rubs in her bedroom in the basement of their home” and started having oral sex with her when she was 16. In total, the documents claim that the 67-year-old abused the girl 50 times.

It’s not clear who the girl is in the documents, as his daughters are too young to be the victim, as the New York Daily News points out. Heidi is now 28, so she would have been only 6 in 1993. Her sister, Holly Montag, is now 31 and would have only been 9. They also have a brother, Sky Montag, who is now 21.

Sources close to Heidi and her husband, Spencer Pratt, say that the couple does know who the accuser is and she is “determined to destroy the family.” They claim the girl has even tried to stalk Heidi and Pratt.

Montag is divorced from Heidi’s mother. He did appear on television in 2009 when Heidi and Pratt were married.

image of Heidi Montag courtesy of INFphoto.com