Police have arrested a 16-year-old Huntington Beach boy who they say was planning to carrying out violent acts at the U.S. Open of Surfing.

The teen was booked into Orange County Juvenile Hall on Friday on suspicion of making terrorist threats, according to a Huntington Beach Police Department news release.

At about noon Friday, the department received a tip from another law enforcement agency about a threat of violence made on social media regarding the U.S. Open, the annual surfing competition, which began Saturday.

Huntington Beach Police Chief Robert Handy said Saturday that the New York Police Department's intelligence division had noticed the post, initially believing it was a threat toward the U.S. Open tennis competition in Flushing Meadows.

The social media post made by the teen was published July 24, according to the release.

Officials are not describing the threat or naming the social media outlet used. However, Handy said the teen previously had published other "disturbing" and "dark" posts, some of which showed him posing with firearms.

Handy said the teen was making the posts using a pseudonym.

"If you look back at lessons that we've learned in law enforcement, like the Isla Vista shooting and other [events], that some of the things that had been posted earlier and all of that, law enforcement pays a lot of attention to those things," Handy said.

"We take them very seriously, so we acted very quickly on trying to determine what this guy's capabilities was, who he was and where he was at."

After police decided the threat to the surfing competition was credible, they began to monitor the boy until a search warrant was obtained.

Investigators served the warrant at the teen's home at 7 p.m. Friday and arrested him. Handy said the suspect told police when he was taken into custody that he was "just messing around."

"We don't necessarily know that for sure," Handy said. "His comment or statement to the officers ... was that he didn't mean it. We're not sure if that's true or not, so that's part of our investigation."

The chief added that the teen had no previous criminal record and that it was unknown whether he had any mental health issues.

Authorities seized a handgun and shotgun in the home. Both were legally acquired by the suspect's family members.

Police also confiscated the teen's electronic devices and are searching them for additional evidence.

Authorities believe the suspect acted alone, according to the release.

In the past year, Huntington Beach officials and event organizers have worked to make the U.S. Open a safe event after a disturbance broke out at the end of the competition in 2013.

Handy said his department has put into place even more measures as a result of the threat.