EVANSTON, Ill. (WLS) -- A student at Northwestern University was attacked Thursday afternoon after a stranger entered her dorm room on the Evanston campus.According to a campus alert, a female student called university police around 4:30 p.m. after an unknown man entered her dorm room in Allison Hall. The student said she argued with the man, and when he fled, she followed him out of her room and confronted him again. At that point, she said he beat her and threatened to shoot her. The student did not report any injuries and no weapon was displayed, the alert said."I was really scared, just being a girl on campus. My gut reaction was to be like, 'Oh, should I be staying here?" said Elizabeth Dickson, who lives in the residence hall.Officers swarmed the building minutes after the incident."I was just walking down, and I saw a ton of police cars, and so that wasn't, I was not comfortable with that," said Dante Gilmer, who lives in the residence hall.Students said a swipe card is needed to access the building and various floors, but somehow the alleged intruder made it into a second-floor dorm room."I assume he kind of followed someone in, and you hold the door for the person behind you. You think you're being polite," Dickson said.University police released a surveillance photo of the suspect. He is described as a black male approximately 6 feet tall, about 210 pounds, with a bald head, no facial hair and wearing a green sweatshirt and blue jeans. He was carrying a gray backpack.Police continue to investigate. They are urging campus residents to report any suspicious activity and not to allow unknown individuals access to the residence halls.Anyone with information is asked to contact the Northwestern University Police Department at 847-491-3456 or the Evanston Police Department at 847-866-5000.