PORTLAND, Ore. -- The suspect in last month's stabbing attack on a Greyhound bus told detectives that he stabbed the driver because he "wanted to make him crash," according to court documents.

Two passengers are credited with protecting the driver and the busload of passengers during the Nov. 29 attack.

The suspect, 32-year-old Robert Vasquez, told detectives he was high on methamphetamine during the attack, court documents said. He also told detectives he was affiliated with the Southside 13 gang in California.

The attack began with Vasquez demanding to be let off the bus while it was on Interstate 84. According to court documents, Vasquez yelled, "If you don't let me off this bus I'll kill you." He then grabbed the wheel, but the driver kept control of the bus.

That's when Vasquez allegedly stabbed the driver in the neck. Francisco Owens and Stephen Danca intervened.

"Without regard for their own personal safety, Owens and Danca forcefully engaged the attacker and the driver was able to safely stop the bus," the Multnomah County Sheriff's Office said in a statement. "The attacker, Robert Moran-Vasquez, was forced off the bus and the driver closed and locked the doors to prevent further incident."

Vasquez was arrested by deputies who arrived at the scene. He made his first court appearance on Dec. 1 in Portland.

Vasquez said little in court but constantly rocked back and forth.

His temporary lawyer entered not guilty pleas to attempted murder, assault and reckless endangerment.

Background: 2 stabbed on Greyhound bus

In California, his mother, Marta Vasquez, told a reporter over the phone that her son was leaving Portland to get a fresh start after breaking up with his girlfriend.

“Had a problem with his girlfriend. He wanted to start over. I don’t know what happened. I really don’t know what happened I had contact with nobody,” she said.

Vasquez is from Fresno. His mother said he has a brother in Idaho.

Vasquez was a passenger on a bus for Boise, sitting right behind the driver, according to other passengers.

The driver’s name is Clint Lawson. His wife Phyllis sent a picture showing the cut across his throat and thanking everyone who helped.

Lawson managed to keep control of the bus as other passengers wrestled Vasquez off him.

Vasquez's mother said he's not violent but court records show he has at least 5 felony convictions.

They stretch back to 2005 and include threatening a witness in a case and a protective order against him that still holds today.

In 2006, he was convicted of possession or manufacturing or selling a dangerous weapon.

in 2007, he was convicted auto theft. And in 2014 he was convicted of carrying a concealed dagger.

There's also still a warrant for his arrest in Indiana for a misdemeanor hit-and-run.