MILWAUKEE, Wis. (WTAQ) - Students at the University of Wisconsin-Milwaukee are put on alert after a female student was sexually assaulted. The students were notified by e-mail about Friday's assault. Milwaukee police say the 21-year-old woman answered a knock on her door and was greeted by a man threatening her with a knife. The suspect is described as 5 feet, 9 inches tall, in his early 20s with short black hair and a stocky build.