Waukesha Police say an illegal alien has confessed to the sexual assault of a physically disabled woman.

Police arrested Juan Carlos Rojas-Sierra, 34, who they say admitted to the crime.

"He ended up confessing to breaking into the apartment and sexually assaulting this woman," said Waukesha Police Captain Mark Stigler.

The crime occurred last month on the 2800 block of University Drive in Waukesha.

"The suspect in this case actually lived in that area and had prior passing contact with the victim," states Stigler. "That's how she knew who she was and where she lived.

"This is not a crime that we usually see in the city of Waukesha. We don't normally have people breaking into someone's home and sexually assaulting them while they're sleeping."

Stigler states that Rojas-Sierra also admitted to being an illegal alien.

"He had been down in Mexico for sometime and apparently couldn't get a visa to get back up here, so he came back up here illegally," says Stigler.

"During that time of him being up here illegally, that's when the assault occurred."

Rojas-Sierra is also on probation for a domestic disorderly conduct conviction. Police are looking into his immigration status at the time of that offense.

"Generally, we'll contact the Department of Immigration's customs enforcement when someone's been arrested for a felony or a serious type of crime," states Stigler.  "We don't call them every time we arrest someone."