It happened this morning at Fremont High - where Food Service Manager Lawana Wyatt was inside serving breakfast.
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She told ABC-7 News, "I was running, telling kids to stay inside, but they wouldn't listen, so I had to scream a lot."
Wyatt says the next thing she saw Oakland police on campus with their guns drawn.
Oakland Unified Schools spokesman John Sasaki told us a student was brought into the office this morning on an unrelated issue with administrators and a school resource officer present. "The student started acting somewhat suspiciously. The police officer asked if the student has any weapons and apparently somehow figured out there was a weapon on this students' person."
It was a loaded gun, in the student's waistband. The officer called for backup and that's when armed oakland police arrived on campus. The school was briefly locked down, but no one was hurt, and the student was taken into custody. Parents and guardians did get a robocall from the district telling them what had happened.
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Lynette Aidoo is one of them. "I was scared because of what happened at the school not too long ago with the 17 kids killed."
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She's of course talking about the deadly shooting last month at a high school in Parkland, Florida. Oakland school administrators say -- in the wake of that shooting, and other incidents - they are working to keep campuses as safe as possible. Sasaki says -- " we can tell people this is our number one priority --the health and well being of our students."
Police are still investigating why the student brought a gun to school. They don't believe he was targeting anyone specific.
Click here for more stories, photos, and videos on recent school shootings across the country.