California school shooting: Student gunned down before ‘teenage shooter tries to avoid detection by blending into class’

A California high school was placed on lockdown after a teenage gunman shot a fellow student before trying to avoid detection by blending into a class, police believe.

The victim, a 16-year-old boy, was shot twice in the upper body in a street outside the school on Tuesday.

The gun attack near Ridgway High School in Santa Rosa, north of San Francisco, prompted a two-hour manhunt.

A 17-year-old has been arrested on suspicion of attempted murder.

Using surveillance footage, officers tracked the suspect to a physical education classroom.

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, Santa Rosa Police said.

The shooter was "behaving normally," and the teacher and other students didn't realize he carried out the violence, Mr Cregan added.

"It's disturbing to see that he was able to go right around to his normal business," he said.

"It's a scary situation."

Police do not yet know if the person who took the backpack and drove away knew a gun had been inside the school.

Authorities said the two students argued before the shooting and believe the violence was isolated.

The victim was in stable condition in hospital.

Witnesses told police that the shooter fired three to four rounds before fleeing, authorities said.

The victim fell down before getting up to run to a vehicle, which dropped him off at a hospital, Mr Cregan said.

Dozens of students were in the area at the time.

Authorities initially said the shooter had an accomplice, but Mr Cregan said the person was released after police determined he was only a bystander.

Detectives were working to figure out if the shooting was gang-related, he said.

Parents described the panic of getting text messages from their kids and not knowing if they were safe.

One mother, Cherie Posluszny, said her 17-year-old daughter texted her.

"Someone got shot," the first message said, followed up a minute later by: "I love you."

"Someone is at Ridgway," read the next message.

Ms Posluszny said she worried about how this "new normal" was affecting children.

"This is becoming routine. It's part of the culture now. These kids are also victims," she said as she raced to the school.

Police said the shooting was originally reported on the Ridgway High campus just before 9 am (local time).

But the force later said it was on the sidewalk just outside the school, which does not have metal detectors.

It is part of a sprawling complex that also includes Santa Rosa High School, Santa Rosa Junior College, school district offices and athletic fields.

The complex with thousands of students, teachers, administrators and others was locked down as a SWAT team searched for the gunman, Mr Cregan said.

Santa Rosa police, who are being supported by the FBI in the investigation, lifted the lockdown around 11:30am following a "thorough sweep" of the area.

School district officials referred questions to police but tweeted that "students are safe."