The unidentified student was freed Friday afternoon, according to Santa Ana police. The case against the suspect was also dismissed.
NOVA Academy Charter School, however, has taken extra precautions and obtained a temporary restraining order that prohibits the juvenile suspect from coming within 100 yards of the campus.
The investigation began after the suspect allegedly sent threatening emails to his-ex girlfriend, who is also a student at the school.
"This ex-girlfriend had received approximately 14 emails from the suspect, talking about his desire to kill students," said Santa Ana Police Cpl. Anthony Bertagna.
While the teen did not threaten the ex-girlfriend, he said that he was going to be shooting at the school and recruit other students to help him carry his plan out, police said. He also apparently told another female student about his plans.
The teen was taken into custody and placed at juvenile hall Wednesday while police continued their investigation. He was released Friday afternoon.
Santa Ana police say the case continues to be an open investigation. The department is working with the school to evaluate their security measures and assess the juvenile suspect's status.
An armed guard will be on campus from 5 a.m. to 10 p.m. Monday through Friday until at least April 11, when students begin spring break.
"We want to reassure students, parents and our staff that NOVA Academy continues to take this threat seriously, remains in constant contact with local law enforcement, and has taken additional security measures to ensure the upmost safety of our school community," a letter sent to parents stated.