A college professor charged with arson for allegedly setting a series of fires at an Orange County high school his son once attended was plotting to kill students and teachers, then burn down the campus after his son committed suicide, authorities said Tuesday.

Rainer Reinscheid, 48, was expected to appear in court Tuesday afternoon after he was charged with five counts of arson, one count of attempted arson and a misdemeanor count of resisting or obstructing a police officer. If convicted, he faces up to nearly 13 years in prison.

Authorities planned to ask a judge that he be denied bail.

Prosecutors said Reinscheid started five fires, including some at University High School, earlier in July.

His 14-year-old son had been a student there and had been disciplined this past spring before he committed suicide at a park preserve.

Reinscheid was arrested last week in connection with the fires and posted $50,000 bail.

After he bailed out, authorities found emails on his cell phone describing a plot to burn down the high school, commit sexual assaults and purchase weapons to murder school officials and students there before killing himself, said Orange County District Attorney spokeswoman Farrah Emami.

Prosecutors believe Reinscheid was acting alone but it wasn't clear if he was targeting anyone specifically.

"I can only at this point tell you, he laid out in sufficient detail plans to purchase guns and murder lots of people," Orange County Deputy District Attorney Andrew Katz told The Associated Press.

After the emails were discovered, Emami said Reinscheid was arrested again.

"The emails by themselves do not support a criminal charge but they do support our argument that he should be denied bail because he's dangerous" Emami said.

Reinscheid is a professor of pharmaceutical sciences at the University of California, Irvine, and has been there for about 12 years, said a university spokeswoman, who referred further comment to authorities.

It wasn't immediately known if he had retained an attorney.

Authorities said Reinscheid is believed to have set five fires and tried to set another, using newspapers, fireplace logs, a book and other items to ignite them.

They said the fires were set on the University High School campus, in the Mason Park Preserve, where his son had died, and at a school administrator's home.

He was arrested at the Mason Park Preserve on July 24 when Irvine police, who had stepped up patrols in the area because of the fires, said they saw him trying to ignite another one.

Irvine Unified School District Superintendent Terry Walker expressed gratitude to the city's police department for making the arrest. He said district officials would cooperate in any way they could.

"These are extremely disturbing allegations, particularly as they involve the potential safety of both students and employees," Walker said in a statement.