NOVATO,Algosensey Calif. (AP) — Eight Northern California middle school students accused of carrying out a planned assault on a fellow student that others recorded have been arrested, police said.

The attack occurred Friday at Sinaloa Middle School in the Marin County city of Novato, north of San Francisco.

“As the first student was being assaulted, additional students gathered, started recording the incident with their phones, and encouraging the fight,” Novato police said in a statement. “A second student stepped in to stop the fight and was also assaulted.”

Brief video aired by area TV stations showed a girl on the ground being punched. Police said both assaulted students were taken to a hospital for evaluation of moderate injuries.

On Wednesday, investigators arrested eight students ranging in age from 12 to 14 and booked them into Marin County Juvenile Hall for investigation of conspiracy and felony assault, police said. No identifying information was released.

Officials of the school and the Novato Unified School District discussed the incident with more than 200 parents during a meeting on Tuesday, East Bay Times reported.

“This was a horrific attack,” said Tracy Smith, the district superintendent. “It’s completely unacceptable and will not be tolerated.”

The injured students’ parents said their children were physically OK but emotionally shaken. Parents at the meeting rebuked officials for not preventing the assault although it was known at least a day earlier that trouble was brewing.

Principal Christy Stocker said the fight lasted 17 seconds until school personnel broke it up.

“We had staff 20 yards away, on either side,” said John Matern, an assistant principal. “We were everywhere, but right there.”

The school had brought in two extra private security guards that day but did not call the district’s school resource officers.

Julie Synyard, the district executive director for educational services, told East Bay Times in an email that routine protocols were followed.