The woman had just left work Monday evening and was in the parking garage at West Lake and North Dearborn when she was attacked.
Police have released security photos of the suspect. The victim, who is recovering from cancer surgery, was in an elevator when a man threatened her with a gun, grabbed her by the neck, punched her and threw her to the ground.
"I screamed for anybody to help me," she said. "Nobody was around, which is unbelievable at rush hour. Nobody was waiting for their cars or anything."
The man ran away with $30 and the woman's cell phone.
