Witnesses saw the child tumble out in his seat, and heard him crying.
"His nose was bleeding," one said.
They said the mother stopped, picked him up and put his booster seat back in the vehicle.
Police said they received several calls about the incident after the mother, identified as Shanéeka Bartley, drove off with the child.
Witnesses asked to call an ambulance, and the mother said she planned to take him to the hospital.
Colonial Heights Police said they discovered who the mother was after they contacted area hospitals, and John Randolph Medical Center in Hopewell confirmed a woman and son had come in for treatment.
"It's insane, I don't understand why someone would not buckle their child up, in a safety seat," said concerned parent Rebekah Bonner. "One you know you're going to get in trouble for it; number two, it's your child, you want them to be as safe as possible."
A friend of the mother said she asked not show her face, but she spoke in defense of Bartley.
"She's a very, very good mom," she said. "She's a hard worker, she takes care of her kids."
Her friend said that at time of the accident, the 32-year-old mother had another child in the car, her daughter -- and that they were happy.
The child was treated for scrapes and released.
Bartley has been charged with child neglect and has been held without bond.