Chino police said the threat was made on Twitter by a 15-year-old Ontario resident who attends the campus.
The teenager, who was not identified, was being held at a juvenile facility in San Bernardino on suspicion of criminal threats, according to Chino police.
The student allegedly wrote tweets such as "I'm recreating Columbine" and "Chino needs a good shooting," according to a group known as "The Tactical Institute," who spotted the tweets and reached out to law enforcement.
No further information was released.