A University of Missouri campus alert was issued Saturday afternoon.
Columbia police say a woman woke up during the night in the 1000 block of Locust Street and found a man in her bed threatening her with a knife. He then sexually assaulted her and ran from her room.
Police say the suspect entered through an unlocked door.
"I just can't believe it. We are all here celebrating homecoming and the fact that something awful happened, you just don't think it could," said Allison Murphy, an MU alum. "We never even think twice about it because this is a really safe area."
Its proximity to campus makes it a popular area for students to live.
"We want to make people aware of it because there are no magic walls around campus that keeps everything out," said Capt. Brian Weimer with the University of Missouri Police Department.
MUPD is working with the Columbia Police Department on this investigation.
There were three roommates home when the man walked into the apartment. Police want to remind all students and everyone living in that area to lock their doors, even during the day.