A 12-year-old girl was in police custody Thursday after a shooting at Salvador Castro Middle School injured four students, two of them seriously.

The gunfire erupted in a classroom at the school in the Westlake neighborhood shortly after the opening bell and caused numerous students to run from the area, according to Los Angeles police Officer Drake Madison.

When authorities responded around 8:55 a.m., they found a 15-year-old boy with a gunshot wound to the head and a 15-year-old girl shot in the wrist and three others with minor injuries.

In a morning news conference, Los Angeles School Police Chief Steve Zipperman said he did not know how a young person got access to a gun and brought it to campus, but warned gun owners to keep their weapons secure and away from children.

"Los Angeles has a law about the safe storage of weapons," L.A. City Atty. Mike Feuer added. "Every responsible gun owner needs to take heed."

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