A 12-year-old girl was arrested Thursday after opening fire inside a Los Angeles middle school, leaving four students injured, authorities said. Two 15-year-olds were seriously wounded in the shooting, hospital officials said in a press conference. Two others suffered minor injuries from what appeared to be grazing wounds. A 30-year-old woman also sustained minor injuries, according to the Los Angeles Fire department. Los Angeles Police officials said they began to receive reports of shots fired at Salvador Castro Middle School at 8:55 am, prompting the school to go on lockdown. Police said the suspect was taken into custody and a firearm, a semi-automatic weapon, was recovered. Law enforcement officials did not disclose what may have led to the school shooting, or if the suspect had any connection to any of the victims wounded Thursday morning.