Last Friday, a suspect shot at the car carrying 6-year-old Aiden Leos, hitting the boy in the back and killing him.
Two Orange County Supervisors and an anonymous donor are matching the reward from the victim's family, putting the total at $250,000.
"It happened in my district, but it doesn't really matter where it happened. This is a young child," said Orange County Supervisor Don Wagner.
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"I would like to match that 50 thousand from our office since Aiden Leos is from Costa Mesa in district two, and it is so important that we find who did I this," said Supervisor Katrina Foley.
Police say Aiden's mom was driving to drop off her son at school at the time of the shooting.
California Highway Patrol officers say they're searching for a newer model white sedan, possibly a Volkswagen.
Aiden's family says a woman was driving, and a man was in the passenger seat.
Tipsters are urged to contact the Highway Patrol by phone at (714) 567-6000, or email at firstname.lastname@example.org.