‘Mommy, my tummy hurts,' says a 6-year-old boy who was shot and killed in a road rage attack after his mother ‘gives the finger' to another driver.

A 6-year-old boy was killed in an apparent road rage attack in California, prompting a police manhunt for the shooter, who has yet to be found.

Aiden Leos, a kindergarten student at Calvary Chapel Yorba Linda, was sitting in a booster seat in the back of the family's car when the incident occurred around 8:10 a.m. Friday. According to police, another driver cut off Leos' mother while they were in the carpool lane, prompting her to give the other driver the finger in the rear-view mirror.

When Leos' mother entered another lane, a passenger believed to be in that other vehicle fired a gun, striking Leos.

“Mommy, my tummy hurts! ” the boy exclaimed, according to his sister, Alexis Cloonan, who described the events during a press conference captured on video by KTTV.

On northbound State Route 55 in Orange, southeast of Los Angeles, the mother pulled over to the side of the road. She cradled the child, and a passing off-duty cop stopped to perform CPR. The paramedics arrived quickly.

Leos was later pronounced dead at Orange County Children's Hospital.

“She had blood on her clothes and then he started turning blue and that’s when the ambulance took him and that was the last time that my mom saw him alive,” Alexis Cloonan told reporters during the press conference on Friday, according to KABC-TV.

She added: “[My mom] had to hold her little boy as he died, so she is very distraught right now."

Investigators are looking for the other vehicle thought to be involved in the incident, a white Volkswagen wagon sedan with two occupants, a man and a woman. While the woman was driving, the man may have fired the gun.

The killing, according to the boy's uncle, John Cloonan, has devastated the family.

“I hope that whoever did this, whoever the friends are of this person, I hope you can see what you’ve done to this family, or what your friend’s done to this family, and please turn them in” John Cloonan said, according to KKTV. “Not that it matters much now because my nephew is dead. We’re never going to be full again.

“My sister has been through a lot. She’s a single mom. And you took her son away. You took her boy away. This boy was full of love and joy and laughter,” John Cloonan said, according to KTTV.

Police shut down the highway for several hours so that investigators could walk the lanes methodically and collect evidence.

Police are asking any motorists who were in the area to assist them with their investigation.

“If your vehicle has a dashcam, we’re asking you, please call our CHP office in Santa Ana, provide that video,” California Highway Patrol Officer Florentino Olivera told KABC-TV. “If you were driving by, you saw something that was not right, call it in – even if it wasn’t something major.”

The boy's sister, Alexis Cloonan, recalled fond memories of her brother, who she said would frequently stop by her room and say he loved her.

“Please help us find the people that did this to my little brother. He’s only six and he was so sweet. He was a very, very loving boy, so please help us find who did this to him,” Alexis Cloonan said at the press conference, according to KTTV.

“He was a rare toddler. I just loved having him in my life.”

A GoFundMe account has been set up to assist with burial expenses. It had raised more than $68,000 as of Saturday morning.

Call the California Highway Patrol at 714-567-6000 if you have any information about the shooting.