"When I saw the car get hit, I saw it starting to come toward us, so I got up and ran and like dove over and hit the fire hydrant, and then the car just plowed into all the little kids," said witness Scott Schubert. "My stepdad and a bunch of guys picked the car up and moved it off to the side to get it off all the kids."
The mother of three of the injured children, 43-year-old Matilda Garnica, was declared dead at the scene, police said.
Six children, ranging in age from 5 to 12, were taken to local hospitals for treatment, three of which were Garnica's children.
Her 12-year-old son was airlifted to Childrens Hospital Los Angeles for a severe head injury. Officials said he is in critical condition.
Authorities said the other children suffered non-life-threatening injuries.
The female driver of the car that ran the red light was not taken into police custody. Authorities said she could face charges.
"We did do a drug test, and we're going to have to wait for the results of that," said Sgt. Richard Cohen of the L.A. County Sheriff's Department.
Police still want to hear from anyone who witnessed the accident. Anyone with information is urged to call the Santa Clarita Sheriff's Station at (661) 255-1121.