The light-colored truck, similar to a two-wheel drive Toyota or Nissan, did not stop after the 9:35 p.m. incident on Green Valley Road west of Ross Road.
Cody Petersen, 24, of Sebastopol, and his two children, ages 1 and 2, were returning from a walk on the West County Trail and were on their way to their car, parked on Green Valley Road, when the pickup came speeding toward them, according to the CHP.
Petersen jumped backward and fell over a guardrail into the Atascadero Creek about 12 feet below, CHP officials said.
The truck struck the left side of the stroller, which was in a bike lane, causing it to overturn with both children still strapped in. Fire and ambulance crews responded in about four minutes.
The 1-year-old girl appeared uninjured but the 2-year-old boy suffered a skull fracture and was flown by REACH helicopter from Santa Rosa Memorial Hospital to Children's Hospital and Research Center in Oakland. Petersen suffered minor cuts and bruises.
The boy was in stable condition this morning, CHP Officer Jon Sloat said.
The pickup had square headlights and a chrome front bumper. Anyone with information about the case is asked to call the CHP at (707) 588-1400.
