A young child was behind the wheel of a vehicle that struck a woman walking a dog in a California crosswalk on Thursday, critically injuring her, police said.

Another young child was also in the vehicle at the time of the crash, according to police, who said both juveniles are under the age of 10.

The collision occurred around 9:30 a.m. PT Thursday in Oakland, according to police.

A family member told ABC San Francisco station KGO that the two children in the vehicle are brothers, ages 7 and 4.

The juvenile driver hit a vehicle before losing control and striking the pedestrian, according to police.

Surveillance video of the incident shows the white vehicle involved in the collision sideswiping a car in the opposite lane, then careening toward the crosswalk that moments earlier a pedestrian had entered with a dog.

The pedestrian, a woman in her 30s, was transported to an area hospital in critical condition, police said.

The vehicle crashed into a retaining wall. The two children inside were also transported to an area hospital and were in stable condition, police said. The 7-year-old has a broken leg, and his brother suffered a concussion, the family member told KGO. 

“The airbags did deploy, so I did see one of the kids fly to the back because when the airbag deployed, it hit him so hard,” witness Lavelle Shah-Marquis told KGO. “These kids were so small.”

Shah-Marquis said he saw the pedestrian lying on the ground.

“To me she seemed really lifeless,” he told KGO.

The boys’ parents were asleep at home when the children took the keys to the car, the family member told KGO.

“Officers contacted the juveniles’ parents, who are cooperating with the investigation,” the Oakland Police Department said in a statement.

ABC News’ Jennifer Watts contributed to this report.