Video from local NBC television showed a line of students walking away from the school
A California high school student on his 16th birthday opened fire on campus on Thursday, killing a 16-year-old girl and a 14-year-old boy and wounding three other teens before shooting himself in the head, officials said.
The suspect survived but was in grave condition, officials said.
After drawing a .45 caliber semiautomatic handgun from his backpack, he opened fire on the other students, and he saved the last bullet for himself, Captain Kent Wegener of the Los Angeles County Sheriff's Department told a news conference.
"At this point, we have no indication of any motive or ideology," FBI Agent Paul Delacourt said.
In addition to the two dead students, two other girls, aged 14 and 15, were wounded, as was a 14-year old boy, Wegener said.
The suspect was described by police as an Asian male and a student at Saugus High School in Santa Clarita, about 65km north of Los Angeles.
The incident marked yet another school shooting in the United States, where repeated mass shootings in recent years have intensified the debate about gun control and the constitutional right for citizens to keep and bear arms.
This is at least the 85th incident of gunfire on school grounds this year, according to Everytown, an advocacy group pushing for stricter gun laws.
Some 2,300 students attend the school, which is made up of more than a dozen buildings.
Sean Murillo, 17, a football player at Saugus High School, said he was walking toward his coach's office when he heard shots about 10 feet (3 meters) away and ducked into a classroom and waited.
Murillo later met his mother at a designated point for parents and students to reunite at Santa Clarita's Central Park.
"There's no feeling of safety until he's in your arms," said his mother, Mercedes Rodriguez.
Taylor Hardges reported seeing people running in the hallways shouting "Run!" She raced into a classroom, where a teacher barricaded the room.
"We've had drills. It doesn't prepare you for the real thing," she said after reuniting with her father at Central Park.
Her father, Terrence Hardges, said she texted him from inside the classroom. He said he was casually scrolling through his texts when he saw it and it made his heart race.
"She said 'I love you. I'm pinned in a room. We're locked in,'" Terrence Hardges said.
Reminiscent of Parkland
The scene at Saugus High School was reminiscent of other recent 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 February 14, 2018.
The Valentine's Day massacre at Stoneman ignited a nationwide student-led movement, calling for school and gun safety. In August, survivors of that shooting released a sweeping gun-control plan that would ban assault-style rifles and take other steps with the aim of halving US firearms deaths and injuries within a decade.
This year marks the 20th anniversary of the shooting at Columbine High School in Colorado, where two teenagers went on a rampage, fatally shooting 12 students and a teacher and wounding more than 20 others before killing themselves.
"Speechless about the shooting in Southern California," tweeted Cameron Kasky, a survivor of the Parkland shooting, who was one of the students who organized rallies and lobbying efforts in Florida's capital Tallahassee and Washington following the shooting.
"Sending love and strength to the whole community," Kasky added.