- A potential plot thwarted. Authorities say it might have been a plan for a mass shooting in Hollywood-- an arsenal in an 18th floor apartment over Sunset Boulevard, thwarted by Los Angeles Police. They were called to this Hollywood high-rise about a man making serious threats. And inside his apartment, they found multiple weapons, high-powered scopes, and more than 1,000 rounds of ammunition. Some of those weapons were loaded and by a window. A suspect is now in custody tonight, an army veteran. And here's our Chief National Correspondent, Matt Gutman, in LA. MATT GUTMAN (VOICEOVER): Tonight, the man accused in a potential mass shooting plot in the heart of Hollywood in court, facing solicitation of murder and weapons charges. The LAPD uncovering this arsenal in a high-rise, saying the rifles were loaded and by a window. - I believe that something tragic here was certainly averted. MATT GUTMAN (VOICEOVER): Officers responding to this building on the famed Sunset Boulevard around 10:00 AM Tuesday, after police say they got a call about a man threatening residents and security, and possibly having a mental health breakdown. The man, identified as 24-year-old Braxton Kyle Johnson, who had been an army infantryman. Officers getting a search warrant and making sure to serve it while Johnson was out. What authorities say they found inside the 18th floor apartment, chilling. RAYMOND VALOIS: When they first went into the apartment in plain view, they observed three rifles and a shotgun laid out on the floor. MATT GUTMAN: As if prepared for something. RAYMOND VALOIS: As if prepared for something, yes. MATT GUTMAN (VOICEOVER): At least some of the weapons neither registered nor legal in the state of California. Also in that arsenal, police say, high-powered scopes putting in range targets hundreds of yards away, including the street below and a dog park. MATT GUTMAN: David, authorities telling me that the suspect had just recently moved into that building. Now, they say they're trying to trace his guns. They're also looking into possible previous arrests in other states. Now, they said they found no manifesto, no writings indicating his intent. But just moments ago, in his first appearance, that suspect pleading not guilty. David? DAVID MUIR: All right. Matt Gutman tonight. Thank you, Matt.