According to Officer Benjamin Granda, a spokesman for the St. Louis County Police Department, the shooting occurred around 8:05 p.m. in the 9800 block of Monarch Drive.
Officers found one shooting victim at the scene. The other victims arrived at the hospital shortly thereafter.
Investigators learned the victims were in a parked car when another vehicle drove by and people in that second car opened fire.
The suspect vehicle was described as a dark-colored passenger car.
Anyone with information on the shooting is asked to contact the St. Louis County Police Department or CrimeStoppers at 866-371-TIPS.