The man, who was also killed in the incident, led Prince George's County Police on a chase, stopping twice to exchange gunfire.
After the man was killed, police found the 3-year-old girl in the car with an apparent gunshot injury. She was taken to the hospital for treatment, where she died.
Police said they believe the girl was the daughter of the driver. They're not sure if she was killed by a police bullet, or shot by the driver.
The man was being chased on suspicion he shot two adults thought to be the girl's maternal grandfather and great-grandmother, police said. The two were taken to a hospital, where they were listed in critical condition.
Police said they believe the man had driven to the grandparents' home in order to abduct the girl.