WILLIAMS, Calif. -- The mother of a bus driver arrested on suspicion of driving under the influence Monday after his casino-bound bus ran into a ditch didn't want her son to drive.

Quintin J. Watts, 52, was arrested at Woodland Memorial Hospital, where he remained in critical condition as of Monday, officials said.

Mother Chaney Mae Watts said she thinks the crash came on her son's first day behind the wheel of the bus after several training trips watching the owner drive.

She and her husband told their son they were uncomfortable with him driving a vehicle that carried people instead of cargo.

"He wasn't the best driver," she said. "He knew we didn't want him to drive."

DMV records show that Watts had been cited for speeding and other violations that resulted in the loss of his license for nearly two years.

He regained his driving privileges last January.

Watts had a commercial license but was not cleared to transport 10 or more people by himself.

In 1981 and then 1983, Watts served time for receiving stolen property, and again in 1996, for check fraud and credit card theft.

In 1998, he spent more than a year in prison for possession of marijuana for sale and possession of a destructive device.

His latest conviction was for possession of a firearm by an ex-felon. He was paroled in Dec. 2007 after almost six months in prison, according to the state Department of Corrections and Rehabilitation.

He was a longtime truck driver, but had been unable to find a trucking job since being released from jail, his mother said.

Watts also served prison time for allegedly threatening his ex-wife last year at her Stockton apartment.

But he had recently started seeing his ex-wife and their three children again.

"He kept to himself," apartment manager Michael Abeyta said. "He was a nice enough guy (and) kept to himself on the property. I never had a problem with him."

Mack Watts said his brother had just started his job as a casino-bus driver and thought his brother had completed the training for the job.

"We do send our condolences to the other families who have lost loved ones and those that are injured," Mack Watts said.

Authorities were investigating whether prescription or nonprescription drugs or alcohol, or a combination, were involved in the crash.

Blood test results are not expected for two to six weeks.

"We believe he was driving under the influence of something. That's why we placed him under arrest," said California Highway Patrol spokesman Robert Kays.

Choua Pau Vang, whose wife Qerlee Vang is currently in critical condition at UC Davis Medical Center, told KCRA 3 that relatives who have taken the bus before have never seen Watts drive the shuttle before Sunday.

"According to my family members on the bus, the driver was new and no one had ever seen him before," Vang said.

Another CHP spokesman, Patrick Landreth, said any criminal proceedings would be on hold while the driver is treated for his major injuries.

The 1993 MCI bus, which was heading to Colusa Casino from Sacramento, was carrying 43 people when it crashed at about 6:10 p.m. Sunday. Up to a dozen passengers were thrown from the bus as it violently flipped before coming to rest in waist-deep mud at the edge of a rice field.

Authorities said 35 people were injured. The CHP earlier said 10 people died, but revised the number to eight.

Sunday's accident was at least the eighth serious crash in the U.S. in the last three years involving buses carrying people to and from casinos.