The victim was taken to a hospital and is expected to make a full recovery.
Sergeant Bob Boese told the OC Register that this appears to be an isolated incident and that the suspect was a former student at the school who ran away after shooting one student. Investigators say the shooting stemmed from a dispute between the shooter and the victim, but are still trying to pin down the exact motive.
"I wish I could tell you what his motivation was or what he was looking to do", McDonnell said.
Sheriff's deputies also received a call reporting shots fired in the vicinity of Manzanita Elementary School about seven miles away from Highland High School.
The implications of US's exit from Iran nuclear deal
First decision is to stay in the agreement if the three European powers - the United Kingdom, France and Germany - ensure the abidance to this deal.
"We are incredibly grateful for the actions of Highland High School teachers and staff and our first responders who courageously protected the lives of our students today", Brett Neal, an assistant superintendent for the school district, said in a statement.
WATCH: Past video coverage of school shooting in the U.S.
Highland High student Katharina Smith, 16, said she was driving to the school when she saw "a ton of police racing toward school".
"Deputies responded immediately to Palmdale shooting, arrest made, weapon found, active investigation underway". "And he's like, 'No mom, for reals, I locked myself up". I heard it at the other side of the school. There was one shot.
Santa Clarita Valley Sheriff's deputies were searching the grounds of Highland High School in Palmdale, the agency reported on its Twitter account. Los Angeles reported one person had been injured.