ORANGE, Calif. (NewsNation Now) — The family of a 6-year-old Southern California boy who was shot to death by another driver in a road rage attack announced a $50,000 reward on Sunday for information leading to the arrest of the killer.

A reward of over $300,000 is now being offered after the Orange County Board of Supervisors voted to contribute, on top of the $50,000 put up by the family.

The mother of Aiden Leos was driving her son to school Friday morning when a white Volkswagen station wagon cut her off on State Route 55 in the city of Orange.

The child was sitting in a booster seat in the right rear passenger side of his mother’s car when he was struck by the gunfire around 8:10 a.m., according to California Highway Patrol (CHP) Officer Florentino Olivera.

His sister Alexis Cloonan said the boy’s mother is “not doing well, because it’s every mother’s worst nightmare. She had to hold him while he was dying.” 

Reyes Valdivia, who along with his wife pulled over to help, said Cloonan told them she “flipped off” the car, and when she started transitioning to the right, the suspect vehicle slipped behind her before one of the occupants fired the shot.

Valdivia told the Los Angeles Times it appeared a bullet had entered the vehicle through the left side of the trunk.

“It went through the boy’s back,” Reyes Valdivia said.

The mother was “hysterical” as she pulled the little boy out of the vehicle after he had been shot, Valdivia recounted. An off-duty police officer stopped at the scene soon after and performed CPR on the child.

Among Aiden’s last words, “Mommy, my tummy hurts,” according to a relative.

Investigators believe a man and a woman were inside the Volkswagen at the time of the shooting.

Olivera described the road rage incident as “isolated” and said it was unrelated to a string of more than 60 BB or pellet gun shootings that have been reported in Orange, Riverside and Los Angeles counties in the past three weeks, mostly along the 91 Freeway. 

CHP asked for assistance from any drivers who were on that section of freeway between 7:55 a.m. and 8:15 a.m., especially if their vehicles have dashboard cameras.

A GoFundMe campaign was set up to raise funds for Leos’ family, and as of Monday afternoon, more than $200,000 in donations have come in.

The Associated Press and KTLA contributed to this article.