Analy High School in Sebastopol went into lockdown briefly Wednesday morning after a person was seen in a school hallway in an outfit that included dark clothing, dark face paint, goggles and carrying a briefcase.
The suspicious person turned out to be a student. He was found in his first period English class, said Analy Principal Chris Heller.
The teen was taken out of the class and the incident was resolved in about 10 minutes, said Heller.
The student was searched and no weapons were involved and there were no signs of criminal intent. The student, who indicated he likes to wear different kinds of clothes, was released to the school, said Sebastopol Sgt. Greg Devore.
The incident started as school was getting underway when a teacher spotted the person in the unusual getup in the school's main hallway.
The person couldn't be identified and it wasn't clear whether they were a student, said Heller.
The teacher told administrators and Heller went to look, hearing the person had gone to the second floor.
Police were called at 7:59 a.m. and the alert was issued for teachers to lock their classrooms, said Heller.
Heller said he would review the incident with administrators and teachers later Wednesday.