By James Jackson, CNN
(CNN) - An out-of-control monster truck crashed into the stands at a show in Oregon, injuring three spectators seated in the front row, authorities said.
Onlooker Dustin Earls captured video of the scene Saturday at the "Monster Air 2012" show in Harrisburg.
Earls told CNN he was watching the third drag race of the event when one of the drivers started heading for a mud pit in front of the seating area.
"The truck got a little wild and he hit the mud pit," Earls said. "I thought, 'This guy's just messing around; he'll hit his brakes right here.'"
But the oversized truck didn't stop. Video shot by Earls on his mobile phone shows the truck making a hard right turn and driving straight into the panicked crowd.
"I heard his axle snap as soon as he hit the mud," Earls said. "As soon as he hit that line, he lost control of his steering and his brakes."
Earls' video becomes jumbled as he runs to safety, but the screams of frightened spectators can be heard in the background.
A Linn County Sheriff's sergeant told CNN affiliate KVAL three people in the crowd were hurt.
Earls said the driver immediately got out of the truck to see if anyone was injured.
"He wanted to know if everything was okay," Earls said, "He was so concerned. He said, 'Oh my God, I can't believe what happened.'"
KVAL reported the driver told authorities the rear wheels on his 1970 Ford spun out in the mud, and he crashed into a barricade. The truck cleared the barricade and its 48-inch tires landed on three spectators, KVAL reported.
The sheriff's sergeant told KVAL the victims' injuries were not life-threatening.