The video shows a person holding a gun near the high school with a caption that read, "UH OH!! Do not come to escuela manana!!"
Police announced that they arrested 21-year-old Rene Alvizo shortly after the post was made on Sunday.
Alvizo has been charged with terrorist threats, grand theft of a firearm, possession of stolen property and several other weapons-related charges.
Police found Alvizo through social media, then pulled him over at a traffic stop.
In the car, police said they found stolen guns, multiple loaded magazines, loose rounds and a ballistic vest.
The driver of the car has been released pending further investigation.
Alvizo's motive is still under investigation.