Updated

A university professor who wrote emails outlining a graphic plan to attack a California high school had been searching for information online about guns, gun laws, ammonium fertilizer and auto explosions in the months before he was arrested on arson charges, a prosecutor said Wednesday.

Deputy District attorney Andrew Katz said University of California, Irvine, pharmaceutical sciences professor Rainer Reinscheid conducted between 40 and 60 such Internet searches on his home computer since March.

Katz said the searches raised authorities' concerns that Reinscheid would follow through on plans allegedly laid out in emails to attack his late son's high school by shooting students and administrators and burning down the school. His 14-year-old son committed suicide after being disciplined at University High School in Irvine.

An amended complaint issued Wednesday charged Reinscheid with eight counts of arson and one count of attempted arson for a series of small fires at the park where his son hanged himself in March, the high school and the home of a school administrator who had disciplined his son.

Prosecutors have not charged Reinscheid with making threats contained in the emails but sought to have him held without bail because of them. He is due back in court Aug. 15.

"The additional searches on the computer, in the people's mind, the prosecution, strengthens the idea that he is following through on the threats that he made in the emails that were previously discovered, and that those threats should be taken seriously," Katz told reporters after a brief appearance by Reinscheid in Superior Court in Newport Beach.

A telephone message seeking comment was left for Reinscheid's defense attorney, Ronald Cordova.