The shooting occurred in the area of Los Robles Avenue and Eldora Road shortly after 3 p.m., according to Pasadena police.
Police say the driver of a vehicle flagged down firefighters and told them someone inside the car had been shot.
The victim was identified as a teen boy from Pasadena. His name was not released.
Police say that victim was taken to Huntington Memorial Hospital.
Police also received a call of shots fired in the area, but investigators say it's not clear if the two incidents are related.
No suspect description was provided.
Further details were not immediately released.