A teenage gunman blended into a classroom after shooting a fellow student multiple times just outside a Northern California high school yesterday.
The attack prompted an hours long lockdown of more than 10,000 students and staffers in a complex with three schools, authorities said.
Using surveillance footage, officers tracked the 17-year-old shooter to a physical education classroom at Ridgway High School in Santa Rosa, north of San Francisco, after a less than two-hour manhunt.
They arrested him on suspicion of attempted murder.
Police Captain John Cregan said authorities were still looking for the shooter's handgun, which he put into a backpack and handed off to someone in a vehicle.
He then went to the nearest classroom, following the school's lockdown protocol.
The shooter was "behaving normally," and the teacher and other students didn't realise he had carried out the violence, Cregan said.
"It's disturbing to see that he was able to go right around to his normal business," Cregan told The Associated Press.
"It's a scary situation."
Police do not yet know if the person who took the backpack and drove away knew a gun was inside.