The sprint car that killed his son Saturday went out of control after the steering wheel came off and the car flew off a dirt track in Marysville at 90 mph, Rob Johnson said Monday.
The winged race car flew about 200 feet into the racetrack pit area, where it struck and killed Marcus Johnson, 14, a student at Rincon Valley Middle School in Santa Rosa.
The driver of the car was Marcus' cousin, Chase Johnson, 17, of Penngrove, an experienced racer and a senior at Petaluma High School. He survived the crash.
Rob Johnson, a former racer who owns a Santa Rosa muffler shop, said he was watching the Saturday night event with his sons and other family members.
Before Chase Johnson took the brand new car onto the quarter-mile clay oval track for warm-up laps at Marysville Raceway Park oval, Rob Johnson said he watched Chase secure the steering wheel's quick-release mechanism, a standard procedure.
"I watched him check it," Rob Johnson said, with an emotional catch in his voice.
The elder Johnson said it is a mystery how the steering wheel came loose.
Undersheriff Jerry Read of the Yuba County Sheriff's Department said Monday that investigators are looking into witness reports that the detachable steering wheel came off, the Associated Press reported.
"It's shaping up to look like a mechanical failure, but there's still work to be done," Read said.
Also killed in the crash at about 6 p.m. Saturday was Dale Richard Wondergem Jr., 68, of Grass Valley.
The two were walking through the pit area when they were struck and killed. Rob Johnson said the car was quiet while it was airborne, evidence that Chase's foot was off the accelerator, and that his son might not have heard it coming toward him.
Rob Johnson said his son was 200 feet from the track, "well removed from any danger area."
In 40 years of racing at dirt tracks across the West, Johnson said he had never seen a car exit through the pit gate in such a manner.
Most race cars have detachable steering wheels that drivers must take off with a quick-release mechanism each time they get in and out of the cockpit, but it's extremely rare for them to come off by accident, said Ron Lingron, the track announcer at Petaluma Speedway, who is a friend of the Johnson family.
"It's a very, very freak accident," Lingron said. "When the steering wheel comes off, you have no control over a car going 90 miles per hour."
Wondergem owned one of the race cars at the track Saturday, but not the one involved in the crash, Read said.
Wondergem is a former sprint car driver who after retirement provided a race car for his son and then for another driver, said Bob Burbach, the announcer at the Marysville racetrack, who said he first met Wondergem 21 years ago.
Burbach told the Marysville Appeal-Democrat that Wondergem was "a kind, gregarious and positively motivated individual."
Wondergem worked for decades with Alf Burtleson, a Calistoga-based contractor who dug dozens of wine caves at Sonoma and Napa wineries and out of state.
Rob Johnson said he was seated in the racetrack grandstand with his younger son, Hayden, and other relatives when the crash occurred. Marcus had left them to go to the restroom. Gina Johnson, Marcus' mother, was not at the track.