The victim remained in critical condition and was "in and out of consciousness," the source said.



According to a release issued earlier by police, the woman was found with no identification about 9:30 p.m. Saturday in the 2100 block of North Rockwell Avenue and was taken to Advocate Illinois Masonic Medical Center. The release said she was in the area to attend a concert at the Congress Theater at 2135 North Milwaukee Avenue, a short distance away from where she was found.



Just as police responded to the scene Saturday night, a security guard from the theater saw three juvenile boys near the victim, and he chased and caught them, according to the police source.



The three, described as being in their mid-teens, were taken into custody.



Chicago police News Affairs Officer Robert Perez said the victim had been found on a lawn on Rockwell Avenue and that she was a sexual assault victim who may have been beaten as well.



Neighborhood resident Danny Medina, 33, woke up from a nap shortly before midnight on New Year's Eve to discover police swarming his street.



From inside the locked gate leading to his home on Rockwell Street, he saw the paramedics lift the girl into an ambulance.



Medina, a 12-year U.S. Army veteran, said the neighborhood where he has lived for 20 years is safer than it used to be.



While crowds attending concerts at the nearby theater sometimes cause problems on his street, Medina said he could not recall an incident as violent and tragic.



"You can still see the blood," he said, pointing to the sidewalk. "It's is very sad."



Anyone with information is asked to call Harrison Area detectives at 312-746-8252.



Tribune reporters Erin Meyer, Rosemary Sobol and Peter Nickeas contributed.



chicagobreaking@tribune.com