MADISON, Wis. -- Madison police are looking for a man who they said walked into a north East Side house and sexually assaulted a woman living there.

Authorities said the incident happened on Jana Lane at about 5:30 a.m. on Tuesday.

Police said the victim was in her home when a man entered through an unlocked door and assaulted her.

Police said the woman was injured in the violent attack, and that she does not know the attacker.

Residents in the neighborhood said they are shaken after hearing about the assault that authorities said happened there early Tuesday morning.

"I'm shocked because this area, I moved here specifically because it was nice, convenient," said Laurel Lotzer, a resident of Jana Lane.

She's lived in her apartment there for four years, and she said this is the first time she's questioned being safe there.

"Overall, I think it is a safe area where you should be able to leave your door open, especially at that time of day," Lotzer said.

But after Tuesday's incident, Madison police are urging residents in the neighborhood and around the city to keep their doors locked.

"The seriousness of this case is the fact that this individual went into a strangers home, violently sexually assaulted her, then fled," said Mike Hanson, a public information officer with the Madison Police Department. "If he's bold enough to do that, he's either done it in the past or he'll do it again the chances are. So we need to apprehend this individual."

Lotzer said that especially because she lives alone, she'll keep her eyes open for anything suspicious and hopes her neighbors will too.

"Perhaps we'll have to band together and look out for each other because it's scary," Lotzer said.

Police said the assailant fled on foot and remains at large Tuesday night.

Authorities have asked anyone with information to call Crimestoppers at 608-266-6014.