A 12-year-old girl allegedly shot two students and injured three other people at Castro Middle School in the Belmont/Westlake area on Thursday morning, prompting a large-scale police response during a national climate of alert over campus gun violence.

Authorities responded to the shooting at 8:55 am Sal Castro Middle, a 6-8 grade school near Belmont High School, just south of Beverly Boulevard near the West 1st Street bridge. As word spread among students about the incident, anxious parents began gathering outside the school awaiting information.

LAPD confirmed the shooting on social media at 9:47 am. The L.A. Fire Department and the LAUSD School Police also responded.

Two student juveniles were shot, one boy and one girl, both age 15, reports said. The boy was listed in critical condition with a shot to the temple. The girl was listed in fair condition with a bullet wound to the wrist. The motive or cause of the shooting was not known known by Thursday afternoon and police said they were continuing an investigation.

KTLA aired footage of the unnamed suspect being taken away from the campus in police custody.

Robert Arcos, commanding officer for the Central Bureau, told the press outside the school that the campus and community were now safe. “As a parent, this is everyone’s worst-case nightmare, a nightmare for all of us,” Officer Arcos said.

Arcos went on: “We know what to do, we’ve trained for it. […] The response from the school district having crisis counselors, administrators here, was nothing short of spectacular work as well.”

Earlier reports said police were also investigating whether the shooting was somehow accidental. [Update, Feb. 2, 9:21 am: LAPD officials said late Thursday authorities do not believe the gunfire was intentional.]

“Our parents who are watching should be assured that their children are in great care,” he added.

The school lockdown was lifted by early afternoon. Later, police confirmed that the suspect in the shooting is a girl of 12. Due to strict privacy laws for minors, no names were released.

Authorities said it was not clear how the 12-year-old got access to a firearm. “Los Angeles has a law about the safe storage of weapons; every responsible gun owner needs to take heed,” Mike Feuer, the L.A. City Attorney, said at a press conference.

The Los Angeles Unified School District released a statement saying that officials were cooperating with police in the investigation.

“We have set up an information center at Beverly Boulevard and Belmont Avenue, where parents, guardians, and community members can receive updates, information about school dismissal procedures, as well as counseling services,” the statement said.

Thursday’s shooting in Los Angeles is one of the earliest grade-school level school shootings of the year, amid increasing concerns over gun violence on campuses nationwide. On Jan. 23 in Marshall County, Kentucky, a 15-year-old gunman shot 16 people at Marshall High School, killing two students, age 15.

Earlier this week, the LAPD released homicide figures for 2017, showing overall killings inside the city kept dropping, but gang-related homicides involving guns were up.