At least one person was killed and three were injured when a gunman wearing black clothing opened fire in the grounds of a high school in California.
The shooting took place in Santa Clarita, north of Los Angeles, minutes before the school day there was due to begin.
Police say a suspect is now in custody.
Many US schools have implemented active shooter drills in recent years, following a string of attacks.
The suspect is a 15-year-old boy.
The suspect is a student at the school.
BBC News reports two male patients were in critical condition, with a third in good condition.
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