Deputies were sent to the school located in the 39000 block of West 25th Street after receiving a report of a man with a gun on campus, Los Angeles County Sheriff's Department Sgt. Bob Boese said.
The incident was reported at about 7:00 a.m., the Sheriff's Department stated in a tweet.
One person with a possible gunshot wound went to a local hospital following the incident, Los Angeles County Fire Department Supervisor Art Marrujo said. The person "self-transported" and was not taken to the hospital by Fire Department personnel, Marrujo said.
A 23-year-old man said he had just left the school after dropping off his two younger brothers and a friend when they contacted him.
"About a minute later, I get a call from them saying there were gunshots," Ricky Munoz said.
About 8:15 a.m., the Sheriff's Department tweeted that they had one person in custody in connection with the man with a gun report.
The suspect, a male, was apprehended near Vons grocery store in Palmdale, CNN reported.
Bureau of Alcohol, Tobacco, Firearms and Explosives officials were responding to a shooting at the school, the agency tweeted.
David G. Millen Middle School, Cottonwood Elementary and Ocotillo Elementary, which are all within 1 1/2 miles of Highland High, were on lockdown during the incident, employees at those schools told CNN.