A driver on a freeway intentionally crashed head-on into a school bus Wednesday, leaving three high-school students and both drivers with minor injuries, authorities said.

The 44-year-old man drove the wrong way on an off-ramp to State Route 60 in Glen Avon and plowed into the bus carrying seven students, Riverside County sheriff's Sgt. Joe Borja said.

The man was seen earlier trying to climb a fence on an overpass of the freeway, and when that failed he got into his vehicle and crashed into the bus, Borja said. His name has not been released.

The sergeant said he did not know whether the man was attempting suicide, but that he could face criminal charges.

Salvador Valdez, an 18-year-old student seated in the fourth row of the bus, said he was stunned to see the car coming.

"It's pretty crazy, you never expect something like that is going to happen when you're on a school bus," he told the Riverside Press-Enterprise.

Another student, Ignacio Flores Jr., 17, said he opened the emergency exit after the crash, stepped out of the bus and saw the man who had hit them.

"He was writhing in pain," Flores told KCAL-TV. "I was like 'Should I help him?' and I'm like 'No forget it, he rammed me.'"

Flores' father, Ignacio Flores Sr., said his son called him and he went to the scene.

"When I saw the accident, I said to myself, 'This is really bad, who would hit a bus full of kids?' he told the Press-Enterprise. "He must be crazy."