Authorities Friday were looking for the driver of a red Honda Civic who reportedly crashed into a motorcyclist on southbound Highway 101 then fled, abandoning the injured rider, CHP officials said.

A CHP officer on the highway near Steele Lane heard the rider yelling for help at 12:02 a.m. and saw Brandon Ashby, 29, of Santa Rosa, leaning against a guard rail, Officer Jon Sloat said.

Ashby’s motorcycle, a 1994 Honda, was on its side in the right lane just north of the Steele Lane on-ramp to the southbound highway.

Ashby was taken to Santa Rosa Memorial Hospital with moderate injuries including what appeared to be a broken ankle, dislocated shoulder and road rash across his body, Sloat said.

Ashby told the officers he was heading south at about 65 mph when he was rear-ended by a car that drove away from the scene. Car parts strewn across the roadway came from a red Honda Civic, likely a model produced between the years 1996 and 2000, Sloat said. The Civic should be missing its left front black plastic inner fender well, its driver’s side horizontal door strip and it may have other damage to the left front side, Sloat said.

Anyone with information about the case can call the CHP at 707-588-1400.

You can reach Staff Writer Julie Johnson at 707-521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.