SAN RAMON, Calif. (KTVU) - The FBI said it is helping San Ramon police after three graffiti messages in one week -- one on a football field and two in the bathroom -- threatened an attack at the school on Thursday.
San Ramon Police Cprl. Mike Pistello wouldn't exactly clarify their role, but said they'd be "circulating" around campus and helping out with extra brain power and resources.
The Bay Area threats comes a day after two teens killed a student at a Denver charter school and wounded eight others.
In San Ramon, Pistello said while police "haven't been able to substantiate a credible threat, we can't say for certain either. It's important we take this seriously and the public knows we take it seriously."
The third threat at Cal High was discovered inside a boys bathroom in the Fine Arts building on Wednesday morning. The graffiti said "Tomorrow the library will be shot up first, then courtyard, and then myself." It also included a racial slur against African Americans.
"There was a racial remark which is also equally disturbing for us. That type of behavior is absolutely not tolerated," said Elizabeth Graswich, the San Ramon Valley Unified School District spokeswoman.
The district notified parents of the threat through email and social media.
"It is concerning," said Erika Atta, a parent. "Whether it's true or not we don't know that. We are planning to stay home. It's always better safe than sorry."
The graffiti is the third threat in the past week. On May 1, a student discovered a message on a different bathroom wall saying there would be a shooting at Cal High on Thursday.
Then another graffiti threat was found at a snack shack near the football field.
School officials say they are working with San Ramon police to track down who wrote the threats, reviewing footage from dozens of surveillance cameras on campus.
"We have 47 here at California High School and we're going to be installing more," said Graswich.
School officials say after the graffiti was discovered Wednesday morning, there was an outpouring of student tips to the anonymous tip line and to teachers.
"The principal went on the loudspeaker and really appealed to the kids for information and we had an immediate response," said Graswich.
San Ramon police will be on patrol at Cal High all day Thursday and say they have put extensive resources into finding the person responsible.
"This is an extensive investigation, so we have detectives and school resources officers as well as patrol officers that were investigating this," said Sgt. Robert Ransom a spokesman for the San Ramon Police Department.
Police say if anyone is doing this as a prank or hoax, it should be clear that posting graffiti and vandalism are crimes with real consequences, and the crime is more severe in the case of issuing threats.
"The actual terminology is criminal threats and it is a felony," said Ransom.