A motorist who lost control of his car while leaving southbound Highway 101 at River Road suffered life-threatening injuries when his pickup crashed and overturned Wednesday afternoon, Sonoma County emergency personnel said.

The unidentified driver was on the southbound off-ramp just before 2 p.m. when he went straight across the T-intersection at River Road, drove up the curb and into some trees, CHP Officer Jon Sloat said.

The full-size truck, loaded with landscaping tools, landed on its roof, the CHP said. The impact caused it to lose two tires and part of the truck bed.

Sloat said the driver may have experienced a medical emergency, causing him to miss the turn.

He was unresponsive at the scene, but paramedics performed CPR, and he was still alive when rushed by ambulance to a local hospital, Sloat said.

No update on his condition was immediately available.

Emergency dispatchers said a dog in the truck survived the crash and was picked up by a Sonoma County Animal Control officer.

You can reach Staff Writer Mary Callahan at 707-521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.