DANVILLE – Patrol officers caught a 51-year-old registered sex offender early Monday morning as he was sexually assaulting a female at knifepoint in her home, according to Danville police.

Deputy Director of Police Doug Miller said at 3 a.m. Monday, Danville police responded to a 911 call that came from a house in the 600 block of Commercial Street. The caller told the dispatcher that a man was holding a female at knifepoint.

When officers arrived, they got into the house and found the intruder, armed with a knife and sexually assaulting a female, Miller said.

Police arrested Johhny L. Wilson, 51, of Danville, who is listed on the Illinois Sex Offender website as a registered sex offender with an address in the 1300 block of Parkview Drive on Danville's southeast side. Commercial Street is on the city's south end, directly west of Parkview.

According to the sex offender website, Wilson's past sex crime that requires him to register as a sex offender was a rape that occurred before February 1978 in Vermilion County when he was 19 years old and his victim was 34.

During Monday's incident, Miller said police found another female in the house who had been tied up before the sexual assault of the victim, and a third female was hiding in a bedroom in another part of the residence. One of the other two females, Miller said, had managed to make the 911 call.

Miller said the intruder evidently got into the residence through a window, because police officers found a window at the back of the house that had been removed.

Miller said Wilson was booked Monday on preliminary charges of home invasion, aggravated criminal sexual assault, unlawful use of a weapon by a felon and aggravated unlawful restraint. He is expected to be arraigned today on formal charges in Vermilion County Circuit Court.

According to Vermilion County circuit court records, Wilson had an emergency order of protection against him in October 2009. There also was an order of protection against him in 2005, and in 2007, he was convicted of possessing a controlled substance and sentenced to 30 months in prison.

Another charge at that same time, aggravated domestic battery, was eventually dropped by the state. Also in 2007, misdemeanor charges of domestic battery were filed against him, but were also dropped.