SANTA CLARITA, CA — A Southern California high school student pulled a .45 caliber semiautomatic handgun from his backpack and fired on fellow classmates on Thursday morning, killing two and wounding three others.

He saved the last bullet for himself. It was his 16th birthday.

The teenaged gunman, whose name was not provided by police, survived the self-inflicted gunshot wound to the head and was in grave condition in hospital, law enforcement officials said.

“Video clearly shows the subject in the quad, withdraw a gun from his backpack, shoot and wound five people and then shoot himself,” Captain Kent Wegener of the Los Angeles County Sheriff’s Department told reporters.

The two slain students were a 16-year-old girl and a 14-year-old boy. Two other girls, aged 14 and 15, were wounded, as was a 14-year old boy, Wegener said.

Investigators said they did not yet know what could have driven the student to open fire at Saugus High School in Santa Clarita, 40 miles (65 km) north of Los Angeles.

Police said the accused shooter had acted alone. Investigators descended on his family home, blocking off the street. They found no further danger there.

A next-door neighbor, registered nurse Jared Axen, said the suspect had seemed introverted, quiet and sad, possibly despondent over the loss of his father from a heart attack in December 2017.

Axen, 33, said it was the boy who found his father deceased, not long after the older man had regained his sobriety and gotten his life “back on track” after years of struggling with alcohol abuse.

“I would say he (the boy) was hurting and couldn’t ask for help,” Axen said of the suspect, who was a track athlete at the school, was involved in Boy Scouts and liked the outdoors, going on hunting trips with his father.

He was of mixed race, born to a Japanese-born mother and White father, with an older sister who became a nurse and moved away.

“I would ask him how school was … he would never bring up concerns of bullying or being a loaner there,” Axen said.

The scene at Saugus High School was reminiscent of other mass shootings at schools across the United States, including the massacre at Marjory Stoneman Douglas High School in Parkland, Florida, where a former student with an assault gun killed 17 people on Feb. 14, 2018.

This year marks the 20th anniversary of the shooting at Columbine High School, where two teenagers went on a rampage, fatally shooting 12 students and a teacher and wounding more than 20 others before killing themselves.

The shooting at Saugus marked the 85th incident of gunfire at a school this year, according to Everytown, a gun control advocacy group. It seems sure to reignite a debate over gun control in the 2020 presidential election.