Speaking exclusively to ABC7, the alleged victim said she was walking alone on the phone with a friend when a man pulled a gun on her.
"I see a man running towards me. Actually running. And he grabbed me," she said. "He took my phone out of my hand and pressed end, and kind of just shoved the gun into my back and grabbed my jacket once again, holding me closer."
After sexually assaulting her, the teenager says the attacker fled, threatening to kill her if she tried to summon help.
"He say when he walked away, listen for when he walked away and make sure he's in the alley because if he sees me getting up, he's going to shoot me and he's going to kill me," she said.
Police are now investigating whether Monday night's assault is connected to a series of attacks -- as many as ten -- on the Far South Side and in suburban Riverdale, Harvey, Dixmoor and Ford Heights.
Riverdale police have released a sketch of a possible suspect and circulated it throughout the south suburb.
Earlier, Riverdale officials said the sketch matched the description of a man being questioned by Chicago police for Monday night's assault. But CPD has denied that report and says no one is in custody.
Many of the victims were targeted outside bus stops and after leaving stores.
"I'm not on the bus coming home no more, so yes I was worried," said Rina Wooden of Riverdale.
Two weeks ago, the spate of attacks was the subject of a forum held by aldermen and suburban mayors.
"My effort is to tell the women of the community to be careful, continue to have their cell phones on hand, if possible walk with someone at all times," said Mayor Deyon Dean of Riverdale.
"Young ladies that's my age, 18, no matter how old you are, you have got to be careful," the alleged victim warned. "I don't want this to happen to nobody else."