Ex-student in custody after shots fired at Perth school

"At the scene police took into custody a 15-year-old male," Commissioner Col Blanch told reporters after the incident.

The boy, understood to be an former student of the private school, is alleged to have fired three shots.

"One of them did hit a school building," Mr Blanch said.

"We believe there were people in the building, we don't know how many."

Officers seized two rifles after the incident from a nearby black four-wheel drive that the teen allegedly arrived at the scene in.

They also found three bullets shells believed to have been discharged from the weapons the boy allegedly fired.

"(He) is now still in custody and assisting police with their inquiries."

"There is no further threat to the community. 

"Everyone is safe and there have been no injuries."

The weapons, a .243 and .22 calibre, were licensed to the boy's home," Mr Blanch said.

"We will look into every aspect during this investigation to understand how a 15-year-old person is allegedly in possession of two long-arm rifles and has shot into a school in these terrible circumstances," he said.

The commissioner described the incident as a rare and shocking incident

"I was very shocked this occurred in WA," he said.

"As police commissioner, I've never seen anything like it."

Detectives continue to investigate the shooting, with the teen's parents yet to be interviewed.

"How does a 15-year-old get hold of two lethal weapons and fire them," Mr Blanch said.

The school was placed in lockdown during the incident, with initial reports saying the teen fired the shots from the school's car park.

Police have commended the school's staff and students for the way they handled the shooting and the information they provided as the shooting unfolded.

Atlantis Beach Baptist College is a co-educational school for boys and girls that started in 2017.

It is located in the suburb of Two Rocks about 70 kilometres north of Perth's city centre.