Officials said a student took a gun to campus in a backpack and entered a classroom to attend a health class. He set his backpack on a desk and the gun discharged.
One bullet was fired, first striking a 15-year-old boy in the neck and then a 15-year-old girl in her temple, according to police. Authorities recovered the gun.
The shooting was reported at 10:40 a.m. The suspect, 17, was arrested, according to the Los Angeles Police Department
Authorities said the suspect was being held at Los Padrinos Juvenile Hall in Downey. They said he had no gang affiliation and no criminal record.
According to people who know the student, he may have taken a gun to school for his own protection for fear of being bullied. He was on probation for an incident last year involving a fight.
The girl was in critical condition and was taken into trauma surgery at Harbor-UCLA Medical Center. The boy was initially listed in serious but stable condition. He was later reported to be in fair condition.
Doctors at Harbor-UCLA Medical Center in Torrance held a news conference at 4:30 p.m. Tuesday.
The girl was struck by the bullet on the left side of the head near her temple. The bullet caused a skull fracture and exited the left side of her head, but did not enter the brain.
The impact of the bullet caused a skull fracture and a brain contusion. She sustained a "fairly significant" blood clot, according to Dr. James Ausman. She was rushed into surgery within 30 minutes of the shooting and doctors successfully removed the blood clot. Her brain swelling was expected to continue for 48 hours.
The girl was recovering from surgery Tuesday afternoon and remained intubated.
According to chief medical officer Dr. Gail Anderson, the boy was in stable and fair condition. The boy was struck first by the bullet. His vital structures were spared and he was expected to survive his injury.
According to trauma surgeon Dr. Scott Bricker, the girl was unconscious when she arrived at the hospital. She exhibited signs of significant brain injury. Ausman said her speech would possibly affected, but better information would be available Wednesday after doctors had more time to assess her condition.
The left side of the brain controls the right side of the body as well as speech.
At a Tuesday afternoon news conference at Gardena High School, incoming LAUSD Superintendent John Deasy said the shooting was an accidental act, but still constituted a crime.
The school is located at 1301 West 182nd Street. Los Angeles Police were on scene with Los Angeles Unified School District Police investigating the situation. The suspect was reportedly apologetic and being interrogated by police at the LAPD Harbor Division station. His mother was reportedly with him. It was also reported the teen suspect is on probation for fighting.
The parents of the two victims were notified. Authorities initially reported three victims.
It was unclear how the student got a gun onto campus grounds. Gardena High School's security consists of handheld metal-detector magnetic wands used by school staff on campus.
The school was placed on lockdown and a perimeter was set up around the campus. An elementary school across the street was also locked down.
Gardena High's 2,000 students were released after the suspect was detained. Students and teachers who witnessed the incident stayed behind to be interviewed by police.
Parents were told to text the zip code 90247 to 888777 for updates. They also can call (310) 354-3400 for more information.
Some parents criticized the school's emergency notification system, which relies on text messages and automated phone calls to parents to give updates and instructions. Deasy apologized for any delays and promised to investigate the system's performance.
According to the school district, Gardena High School will be open and is expected to operate on a normal schedule on Wednesday.