It happened at about 7:45 a.m. local time near Booker Middle School in Sarasota, a Florida Highway Patrol report said.
The police report said a vehicle stopped in the right turn lane to drop off a pedestrian, who got out on the passenger side and dropped markers and pens.
That's when the pedestrian bent down to pick her items from under the vehicle, and the vehicle's driver began to move forward, hitting her, the report said.
WFTS in Tampa Bay reported that the pedestrian is a 12-year-old girl, and the driver is her mother.
"She immediately stopped when she heard her child screaming," FHP Trooper Kenn Watson said, according to WFTS.
The police report said the girl was transported to Johns Hopkins All Children's Hospital with critical injuries.