SOUTH PASADENA, Calif. — Police say they have arrested two teenage boys who were planning a mass shooting at their Southern California high school.

South Pasadena police Sgt. Brian Solinsky said the two students from South Pasadena High School were taken into custody Monday.

He said police learned Thursday of a specific plan to kill three staff members and gun down as many students as possible.

Solinsky didn’t say what form the plan took, only that police were informed through the school district. He said the boys possessed no weapons yet but were trying to get them.

Police said the boys had been under constant surveillance since Thursday, and police served warrants at their homes Monday.

He said one of the boys tried to run but was immediately caught. The other was arrested without incident.