A motorcycle rider crashed Sunday afternoon while on a ride with a large group of motorcyclists in northern Sonoma County and was flown by medical helicopter for treatment, according to the CHP.

The 55-year-old man crashed at about 12:50 p.m. near Highway 128 and Chalk Hill Road, according to the CHP.

A nurse, either in the riding group or who stopped to help, performed CPR on the man, according to initial reports.

A REACH medical helicopter was called to the crash scene, and the man was flown to Santa Rosa Memorial Hospital.

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