The little girl was in a rental car traveling south in Opa-Locka, WFOR-TV reported.
"The mother was inside that vehicle, along with the child and the child was struck," Detective Robert Williams said.
Police were called and the child was rushed to a hospital, where she died from a head wound.
Williams said detectives were at the hospital talking to the mother.
"She is very distraught, her child is dead. Investigators are there now trying to get information from her," Williams said.
"Homicide investigators are also in the area talking to residents and to witnesses to try and find out if that vehicle was targeted or if it was accidental shots that went off," he said.