The rocker was performing in Toronto, Canada on 21 December (14), when he stopped the show to berate the audience member.
He said, "Hey, you wanna f**king stop the show? That's my f**king mother right there, you jack-off. I'm gonna f**king beat your f**king face in.
"Don't f**k around with my f**king mother if you f**king wanna get out of here alive. Don't anybody f**king touch my f**king mother or I'll jump right the f**k in here..."
Bach then asked his mum if she was Ok, before adding, "Any more idiots, man, and I'm f**king outta here. We're here to have a good f**king time, right? She's 70 f**king years old."
It is unclear whether Bach's mother was pushed or if someone was pushed into her.