A Petaluma boy on his way to a boating birthday party at Lake Mendocino died Friday after his host's truck ran out of gas on the freeway and party guests were helping to push the vehicle down the offramp, the CHP said.

The 13-year-old boy fell between the pickup and the boat trailer as the vehicle gained momentum heading downhill, authorities said.

The youth, identified by officials as Trevor Smith, was run over by the trailer and suffered fatal injuries in the 10:24 a.m. accident, authorities said.

The driver of the truck was Michael Krnaich, 41, a Petaluma resident and owner of Ramp Rats, an indoor BMX bike and skateboarding facility off Piner Road in Santa Rosa.

The CHP said Krnaich was driving a 2010 Chevrolet pickup towing a ski boat and carrying several children headed for his daughter's birthday celebration when he ran out of gas on northbound Highway 101 near the West Lake Mendocino Drive off-ramp.

Those in the car, and possibly some passers-by, got out to help push the truck toward the off-ramp, which heads downhill toward a Chevron gas station, authorities said.

Some children were positioned at the tailgate of the pickup and began to jump into the bed of the truck as it picked up speed.

The victim, a friend of Krnaich's daughter, may have jumped up to the bumper or onto the tongue of the trailer before jumping into the bed of the truck, and lost his footing doing so, authorities said.

He fell onto the pavement and was run over by the trailer, CHP Officer Steve Krul said.

Those at the scene used CPR to try to revive him while awaiting paramedics, but the boy was pronounced dead at Ukiah Valley Medical Center, the CHP said.

Krnaich said Friday, "I love kids. My whole life has been dedicated to kids. Mine and others. I have taken more kids on trips than anybody I know. And to have something like this happen is devastating."

He sent an email in response to an inquiry to his Facebook site.

"My heart goes out to the boy's family. And words cannot describe how I am feeling," he stated.

"I am a good person. A father, husband, son, brother, uncle, coach and mentor to many in my path over the last 10 years of running Ramp Rats."

You can reach Staff Writers Mary Callahan at 521-5249 or mary.callahan@pressdemocrat.com and

Clark Mason at 521-5214 or clark.mason@pressdemocrat.com.