The victim was shot just before school started while he was walking through a lunch area.
A 17-year-old suspect was taken into police custody at South East High School, located about a mile away in the city of South Gate.
Crisis counselors were on hand and extra security was added at the South Gate High School campus. Police poured onto campus after the incident Tuesday morning. The result was a very quick arrest. The 17-year-old suspect was detained within an hour of the shooting.
The alleged gunman had no problem entering the school. Gates are all open before class. There is no check for identification. According to eyewitnesses, the suspect looked like any other student.
"This guy was covered, had a black sweater, had his hood on but his face was all covered and basically he went inside like a regular student, he even had a backpack and everything," said "Stephanie," a student.
It was on a blacktop area that the suspect pulled a gun, appearing to target a single student.
"We just saw a kid pass by and turn back halfways and he just shoots," said student Robert Angulo.
"He ran out. He bumped into two teachers," said Stephanie.
His exit was speedy but his collision made him easier to identify. He appeared to be a former student at South Gate High who had transferred to South East High, one mile away. And that is where he ran. School police radioed officers stationed there. They collared him as he arrived.
"I am texting my son, 'Please just text me back and tell me you are OK'," said parent Lizet Morales.
South Gate High was on lockdown for an hour until the suspect was arrested.
The victim was grazed by the bullet. He was released from the hospital just before noon.
South Gate High's principal says stopping an intruder from another school is virtually impossible.
"We don't have the personnel to supervise every single student and check for IDs; we don't check for IDs," said South Gate High School Principal German Cerda.
But Cerda says there are random checks for weapons and drugs.
"They take everybody out and check their backpacks and pockets and all that," said Luis Acosta, a senior South Gate student.
"I am an alumni here of South Gate High School. "To be honest, we have never had any problems -- not like this inside the high school," said Lizet Morales.
"I still feel safe. I don't feel any worries," said Luis Acosta.
Police spent most of the day with a K-9 unit looking for the weapon. As of 2 p.m. Tuesday, they still had not found
The motive for the shooting was still under investigation.