Attackers shot two students near a San Francisco Bay Area high school, killing one and sending another to a hospital in an incident that prompted the closing of the campus, authorities said Thursday.

Both victims were students at Novato High School, Marin County sheriff's Lt. Doug Pittman said.

Their names and ages have not been released. Both were shot and one was stabbed Wednesday evening.

Pittman would not say if arrests had been made. A motive was not known.

Police say the attack occurred on a hiking trail at the edge of a country club community. Pittman says there is no threat to the community because it was an isolated incident involving a small group of people.

Still, Novato Unified School District shuttered the campus on Thursday to ensure the safety of students and staff, and because of uncertainty about the situation, according to a letter sent to parents.

The school will also be closed Friday due to a pre-arranged staff development day. School psychologists and counselors will be available Tuesday to assist students who need assistance after the long holiday weekend.