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A 26-year-old Northridge man who allegedly had an assault rifle was arrested on suspicion of making a threat that prompted the temporary evacuation of Pierce College in Woodland Hills Thursday.

Evacuations began about 8:30 a.m. and classes did not resume till 3:30 p.m., by which time authorities had found firearms and ammunition at the home of the man they suspected of making the threat.

Students were asked through the school’s Facebook and Twitter accounts not to come to campus and to spread the word that the campus was being evacuated.

Several patrol cars were seen at the school as authorities searched for any possible threats, aerial video from Sky5 showed.

Police conducted the investigation after a threat was made on social media claiming that an armed gunman might come to the campus, the school posted on its Facebook page.

The post also stated that students should “not become overly concerned, but to calmly evacuate the campus.”

At about 12:30 p.m., Nicole Nishida of the Los Angeles County Sheriff’s Department stated that a 26-year-old man had been arrested for allegedly making the threat.

Later, the Sheriff’s Department identified him as Sergio Castanon Jr., a resident of Northridge.

At Castanon’s home, detectives found an assault rifle, handgun, several rounds of ammunition and illegal high capacity magazines, according to the Sheriff’s Department.

He was taken into custody about 11:45 a.m. and was being held on $50,000 bail on on suspicion of criminal threats, possession of high capacity magazines and illegal ammunition.

In a statement released late Thursday, school officials said Castanon, a former Pierce College student, never made it to the school on Thursday.

UPDATE ON EMERGENCY ALERT: THE CAMPUS WILL REOPEN AND CLASSES WILL RESUME AT 3:30 pm today. Note there will be… http://t.co/ikWUG3sofY — Pierce College (@PierceCollegeCA) October 16, 2014

EMERGENCY ALERT * PIERCE COLLEGE IS BEING EVACUATED DUE TO AN UNKNOWN THREAT. * DO NOT COME TO CAMPUS * Please… http://t.co/boYuFriBWr — Pierce College (@PierceCollegeCA) October 16, 2014