12-year-old girl in custody after 'accidental' school shooting: Police

— -- A 12-year-old girl is in custody after four classmates were injured in a shooting at a Los Angeles middle school Thursday morning, authorities said.

A 15-year-old boy was shot in the head and was in critical-but-stable condition, while a 15-year-old girl was shot in the wrist and in fair condition, the Los Angeles Fire Department said. The two other children suffered minor wounds and were treated and released.

A doctor treating the 15-year-old boy at LAC+USC Medical Center said he expects him to make a full recovery.

The shooting is believed to be accidental, the Los Angeles Police Department told ABC News. The suspect, who hasn't been identified, was booked into L.A. County Central Juvenile Hall for the negligent discharge of a firearm and is being held without bail.

A gun was recovered, no suspects are outstanding and the Salvador B. Castro Middle School has been declared safe, the LAPD said.

One parent told ABC Los Angeles station KABC-TV that the shooting took place next to her son's classroom.

"He was in tears, but I'm so thankful he picked up the phone," she said of her call to him.

Diego Salinas said when his sister texted him from the middle school, he immediately rushed over.

"I went crazy, I couldn't handle it," he told ABC News. "I'm actually shaking ... I'm really afraid."

"I'm nervous, I'm anxious, I want to cry," Salinas added.

How the gun was obtained is under investigation, but L.A. city attorney Mike Feuer said this is a "call to action" for every adult who has a gun.

"You must store it safely and keep it out of access for any child to reach," Feuer said.

The shooting was reported at 8:53 a.m. local time and occurred in an elective class with mixed grades, officials said. The school was placed on lockdown, which later was lifted.

Classes continued as scheduled on Thursday, and Friday would be a normal school day, officials said.

The middle school is located on the Belmont High School campus and has about 365 students in grades 6-8.

"Our thoughts and prayers are with those who were hurt in today’s shooting incident at Sal Castro Middle School and with all the students, families and employees on the campus," Vivian Ekchian, interim superintendent of the Los Angeles Unified School District, said in a statement.

"The Los Angeles Police Department, Los Angeles Fire Department, Los Angeles School Police and District leadership immediately responded, and we followed protocols to ensure the safety and well-being of the Castro Middle School community," she added. "The school has been declared safe, and we are communicating with parents of students at Castro Middle School, as well as neighboring campuses. We are also providing appropriate supports to those who may be impacted by the incident."