CHICAGO (CBS) — A man groped and battered a Northwestern University student in an elevator Tuesday night in north suburban Evanston.

At 9:37 p.m., police responded to an apartment building in the 1900 block of Ridge Avenue for a report of attempted sexual assault, according to a statement from Evanston police.

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The victim, a 24-year-old woman, said she saw a man knocking on the entrance door to the building, police said. Thinking he lived in the building, the woman opened the door and got into the elevator with the man.

He then began to grope her and tried reaching under her clothing, police said. The woman began to scream for help when the man beat her up and threw her to the floor.

Once the elevators door opened, the man ran away with her wallet and cellphone, police said. The woman suffered scrapes to her legs, but refused medical treatment.

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The offender is described as a black man between 25 and 30 years old, between 6-feet and 6-foot-4 and weighing 190 to 230 pounds, police said. He was wearing a dark long-sleeve shirt, dark pants and carrying a backpack.

Evanston Police Cmdr. Joe Dugan says residents should not let strangers into their building.

“As rude or un-neighborly as it might be, you should not open up the door,” he tells CBS 2’s Jeremy Ross.

Anyone with information should contact the Evanston Police Department Detective Division at (847) 866-5040.

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