Agents seized more than 1,000 weapons at a home in one of the richest neighbourhoods in the US, authorities said on Wednesday night.
A suspect was in custody soon after.
The man, whom Los Angeles police later identified as Girard Damien Saenz, 57, was held on suspicion of unlawful transportation and giving, lending or selling an assault weapon, said Lt. Chris Ramirez, a police spokesman. Saenz was released on $50,000 bond on Thursday.
Police alongside agents of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives discovered the rifles and pistols while serving a search warrant at the residence in the Holmby Hills area of west Los Angeles.
Many famous performers and artists have made Holmby Hills their home, among them Michael Jackson, Neil Diamond, Frank Sinatra, Barbra Streisand, Bing Crosby, Gary Cooper, Walt Disney and the power couple of Humphrey Bogart and Lauren Bacall.
Authorities valued that private collection at a $500,000 to $1 million.