The car was found at 10:30am on the 15300 block of Market. First responders extinguished the flames, then found two bodies in the vehicle's trunk. Two additional bodies were found in the backseat.
Authorities say the deceased are all African American adults, but have not been able to determine their identities. Two are male and two are female.
Foul play is suspected. Police say the victims were dead before the fire was set.
"It was mainly confined to the front of the vehicle," HCSO Deputy Thomas Gilliland said of the fire. "Whatever they tried to burn -- it didn't burn very well."
The investigation is ongoing.