No charges have been filed in what appears to be a targeted attack. Police have not released a motive or said if the suspected shooter is one of those "persons of interest" being questioned.
"There was one shooter, and he was by himself. The other individuals, we're not sure what part they may have played in the incident," Chief Mark Turkey, Romeoville Police Department, said.
Police said the gunman opened fire as the woman, 33, and her daughter, 15, got into an SUV around 7 a.m. Thursday in the 300-block of Emery Avenue. Witnesses said a man fired two or three shots into the vehicle.
''I heard two gunshots, and I opened up my back door to look out, and I heard somebody screaming, and I ran out the front door and I saw her getting out of the driver's side, and she was holding her chest. So I ran over there, and she just had blood pouring out,'' said Brian Corban, the victim's neighbor.
Police say the suspect fled the scene on foot. Romeoville schools were on soft lockdown for several hours before being allowed back in the school around 10 a.m.
Neighbors say the family was new to the area. Both mother and daughter remain hospitalized in serious condition.