McCarthy said a third person — an adult — was taken into custody but hasn’t been charged. Police are investigating whether that person or the 17-year-old may have brought the gun to the scene of the fight.
The girl charged was represented by an attorney with the county’s public defender office, which declined comment.
McCarthy said the gun was reported stolen two weeks ago from a car parked in another South Side neighborhood. Part of the police investigation includes tracking how that weapon ended up being used in a homicide.
Chicago’s battle with violent crime has been closely watched. In 2012, it led the U.S. in homicides with more than 500. It ended 2013 with 415 homicides — the lowest total in nearly half a century but still far more than any other U.S city, including much larger Los Angeles and New York.
The overall crime rate fell last year to a level not seen since 1972, and the number of shooting incidents involving victims 16 and younger dropped 40 percent in 12 months, city officials say.
Last Friday, a 32-year-old Chicago woman named Leonore Draper was shot to death after attending a fundraiser for an anti-violence group. Police said she was apparently caught in rival gangs’ crossfire and was not the intended target.