A Southern California man barged onto an elementary school bus carrying about a dozen children and held a knife to the driver's head before witnesses dragged him away, authorities said.

The man boarded the bus early Friday morning in the community of Campo when the driver saw him approaching and thought he was a parent trying to hold the bus for a child running late, the San Diego Union-Tribune reported Saturday.

"He turned around and I saw the knife," said Jesus Jimenez, a sixth-grader who helped usher screaming children off the bus through the rear emergency exit.

Parents and others helped the children escape. One parent flagged down a passing driver who jumped on the bus and helped pry the knife from the man's hands.

No one was injured, said sheriff's Sgt. William Uelen.

Authorities arrested Matthew Barker, 37, of Campo for investigation of assault with a deadly weapon. He was previously known to authorities and had drug issues, Uelen said.

After fleeing, the children ran to their parents outside or ran back to their homes. They were taken to school on another bus, school district officials said.

Uelen said they were brought to a classroom where they could be calmed down.

Jesus' mother, Dania Jimenez, said she's proud of her son's quick thinking and action to help get people out.

"Imagine if they hadn't opened the door," she said. "They would've been stuck in the bus."

Campo, which is in San Diego County, is roughly 173 miles (278 kilometers) south of Los Angeles.