MILWAUKEE -- An Oak Creek man, accused of sexually assaulting a UWM student, has been arrested.

Police say the 31-year-old is a registered sex offender, who befriended the 21-year-old victim and then attacked her inside her own off-campus apartment on Maryland Avenue.

According to the police report, the victim and her two friends were returning home after celebrating her birthday. The suspect was parked outside and followed them in, introducing himself and even wishing the victim a happy birthday. He then waited outside the woman's apartment door until her friends left and then knocked on the door. When the victim opened, he allegedly let himself in and then forced her at knife-point to perform sexual acts. The victim told police the suspect then ran out when her roommate came home 15 minutes later.

The suspect was picked up at a south side motel Friday night and is being held in the Milwaukee County Jail on $50,000 bail. Police say it does not appear he knew the victim he is accused of assaulting.

According to court records, the suspect is no stranger to the law. As recently as 2007, two women tried to get restraining orders against him, and back in 1999 he was convicted of third-degree sexual assault, which landed him on the sex offender registry.