The lockdown at the school was lifted several hours after the shooting and school officials said they would begin reuniting students with their parents.
Authorities in Southern California say their response to reports of shots fired at a Palmdale high school worked.
The sheriff's office tweeted one suspect has been detained in connection to "the person with a gun.at Highland High school in Palmdale".
The department added that the suspect was arrested off-campus and a rifle was recovered off-campus, and the shooting appears to be an isolated incident with no further threats to the community. The campuses were searched and no incidents of concern were reported, the superintendent later said.
Nadine Luke told CNN her 18-year-old daughter called her, screaming, after she heard shots in the school.
The motive for the shooting is unknown and it's unclear whether it is gang related, Schrader said. They suggest it could have kept the situation from getting worse.
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Santa Clarita Valley Sheriff's Office deputies were searching the grounds of Highland High School in Palmdale, Officer Nicole Nishida, spokeswoman for the Los Angeles County Sheriff's Office, told ABC News. "The student said he was only joking, but deputies later found two semiautomatic rifles, two handguns and 90 high-capacity magazines at the student's home".
"I thought he was joking, and I'm like, 'Don't mess around, that's not amusing, '" said mother Ana Salazar.
Students on the campus remained calm and texted their classmates, telling them to stay away from the area, and faculty members directed deputies throughout the campus, allowing them to clear the building faster, McDonnell said.
Bureau of Alcohol, Tobacco, Firearms and Explosives officials also responded to the shooting, the agency tweeted.
The shooting was reported at Highland High School in the town of Palmdale, 40 miles north of downtown Los Angeles, CBS Los Angeles said.