Los Angeles police prevented a possible mass shooting and seized a weapons cache in a raid on an apartment where they found rifles pointed at a public park in the city.
Mr Johnson was arrested on a complaint of making criminal threats, according to KTLA.
And when officers searched an apartment at Lumina Hollywood, they say they found high-powered rifles, handguns, shotguns and ammunition.
“The suspect was located on the 18th floor of an apartment building with large windows with a view, with a non-obstructed view of a public park, downstairs, and some of the rifles were pointed outside of the windows,” LAPD Lt. Leon Tsap told the station.
And he told ABC7 that “there is a high chance that the officers, and obviously, security staff and the people who called, prevented a mass shooting from happening.”
LAPD shared a picture of the weapons and body armour they discovered on Twitter.
Authorities said that Mr Johnson had been threatening people outside the location and credited vigilant neighbours for raising the alarm.
Police said that none of the weapons are registered to the suspect and that two of the weapons were reported to be illegal in the state of California.
Mr Johnson, who investigators say lived alone and had recently moved from the east coast, was held on $500,000 bail.
A resident at the building, who wished to remain anonymous, told CBS News that the suspect had made threatening comments to him earlier in the week.
“He kept talking about mass shootings, and then at one point he asked me, ‘I wonder how many people I can snipe through my floor,’ and he lives on the 18th floor, so in my head, I’m like ‘Oh my God, is he like planning on shooting us, or planning on shooting people at the park?’” said the male resident.
“And then he kind of like took two steps back and made a comment like, ‘If I was the police, I would start my investigation right here.’”
The Los Angeles County District Attorney’s Office will review the case and bring any charges.