Story highlights Four students and one adult were hurt, authorities said

The shooting appears to be isolated incident, police said

(CNN) A 12-year-old girl faces two felony counts in connection with a shooting at a middle school that left four students and an adult injured, the Los Angeles County District Attorney's office said Friday.

Warrants will be issued for being a minor in possession of a firearm and bringing a weapon on school grounds, the DA's office said in a statement. She is expected to be arraigned Monday.

The girl, being held in Los Angeles County Central Juvenile Hall, was also booked for negligent discharge of a firearm, authorities said. The incident involved a semiautomatic weapon, which was confiscated, Los Angeles Police Lt. Chris Ramirez said.

Police earlier said the Thursday shooting was "unintentional." Police didn't say what led to the shooting, which unfolded at the Sal Castro Middle School in the city's Westlake district.

While "negligent" use can cover a variety of activities, it most likely refers to "mishandling" in this case, Ramirez said.

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