They younger girl was shot in the right thigh while the older girl was shot in the right hand. Eddie Johnson said in a press conference. Police said they were not the intended targets.
Johnson - in a familiar refrain - said the city's elected officials weren't doing enough to stop the violence. Fire Department spokesman Larry Langford says he thinks both girls are students at the school.
Police spokesman Frank Giancamilli says the injuries aren't considered life threatening.
Police stopped a vehicle linked to the shooting nearby a short time later and were questioning the occupants.
The hospital says the girls' families have asked that no details about their conditions be released. Former students at the school tried to enter the picnic, but school security did not let them in, Supt. Students who had been suspended from the school were trying to attend the picnic.
CHICAGO, Ill. (CBS/AP) - Two children have reportedly been shot on a playground outside a Chicago area elementary school.
According to a CNN tally, at least 16 people were shot in Chicago between 3 p.m. Thursday and 3 p.m. Friday.