The spray-painted message on a wall near two Santa Ana schools threatens violence against Brown.
"They chose a high-visibility location. This would be someone trying to get attention initially, but in doing it in such a way to create fear in society," said Santa Ana resident George Collins.
Police consider the threat against the newly elected governor a terrorist threat.
"We're taking it extremely serious considering what occurred in Tucson as well as the rash of incidents that have occurred recently, not only in our city but other cities in Orange County," said Santa Ana Police Corporal Anthony Bertagna.
This month at least eight hate-speech messages filled with spelling errors have turned up in four different cities in Orange County. In Anaheim Hills there were threats of violence against Mexican, Asian, African-Americans and Catholics.
In Brea, outside two stores, racial epithets aimed at Chinese and African-Americans were spray-painted.
In Anaheim, crews removed hateful graffiti from a wall near a bank and off an abandoned store.
At St. Thomas More Catholic Church in Irvine, more graffiti was spray-painted on the walkway.
At St. Boniface Roman Catholic Church in Anaheim, a similar message was spray-painted. Police are reviewing surveillance video from the church parking lot that shows a white minivan driving in. On the video, the driver gets out and heads toward the church. Minutes later, he or she walks back to the van and leaves the area.
Police departments are working together to determine if the cases are related and if there is any significance to the date listed on the latest threat.
If you have information related to the incidents, you're asked to call Santa Ana Police at (714) 245-8390.