Authorities are searching for witnesses of a hit-and-run crash Saturday in Graton that left a 2-year-old child with major head injuries, CHP officials reported.

Cody Petersen, 24, of Sebastopol was pushing his son and one-year-old daughter in a stroller from the West County Trail to his parked car along Green Valley Road when he heard a speeding vehicle coming their way at about 9 p.m., Officer Jon Sloat said.

The father saw a light-colored pickup heading westbound on Green Valley Road heading toward them, Sloat said.

As the car beared down on them Petersen jumped back, fell over the guardrail and landed about 12 feet down in Atascadero Creek, Sloat said.

The truck struck the left side of the stroller, knocking it on its side with the two children strapped inside, Sloat said.

They were transported to Santa Rosa Memorial Hospital where doctors found that the boy had a fractured skull, Sloat said. He was flown to Oakland's Children's Hospital.

The daughter appeared uninjured and the father was treated for cuts and scrapes from the fall, Sloat said.

The hit-and-run vehicle was described as light in color, with square headlights and a chrome front bumper. The pickup looked similar in style to a two-wheel-drive Toyota or Nissan, Sloat said.

Anyone with information about the collision can call the CHP at 588-1400.