Marilyn Manson Calls Gun Stunt an 'Act of Theater'

Marilyn Manson was just creating art when he pointed a police-approved fake gun into the crowd at his San Bernardino concert.

Manson defended the stunt, which came almost 2 years after the San Bernardino terror attack ... calling it an "act of theater" about how easy it is to get semi-automatic weapons.

Manson said, "My art has always been a reaction to popular culture and my way to make people think about the horrible things that happen in this world." He claimed to have police approval to use the prop, and added ... "My performance was not meant to be disrespectful or show any insensitivity."

The San Bernardino Sheriff's Dept. tells TMZ it did NOT approve or disapprove of Manson's stunt. However he did give them a heads up he was doing it, which they appreciated ... so deputies at the venue weren't caught off guard.