Video obtained by TMZ early Monday shows Manson pointing a toy rifle at the audience at the Glen Helen Amphitheater during a show Sunday night while performing "We Know Where You F***ing Live." Manson was in a wheelchar, since he broke his leg during an on-stage accident in September.
Manson later said the stunt was meant to be a comment on the frequency of mass shootings in the U.S. Hours before his performance, 26 people were killed at a church in Texas.
"In an era where mass shootings have become a nearly daily occurrence this was an act of theater in an attempt to make a statement about how easily accessible semi-automatic weapons are and how seeing them has become normalized," Mason said in a statement to Rolling Stone.
"My performance was not meant to be disrespectful or show any insensitivity," Manson added. "The prop microphone I used on stage was handed to me with the approval of a police officer."
The San Bernardino Sheriff's Department told TMZ they did not approve or disapprove of the stunt. Mason did tell them, so deputies at the event were not surprised.
Fourteen people were killed and 24 others injured at the Inland Regional Center in San Bernardino on Dec. 2, 2015.