A mentally retarded guy lives together with his mother who keeps him from leaving the apartment claiming the air outside is poisoned. Whenever she goes outside she is taking a gas mask with her. After his mother had died he kills his cat by wrapping it in a plastic foil. He keeps the dead cat for some time and still would not leave the apartment. He finally goes to town, not able to talk, meeting several people. Next thing I remember is that he becomes a member of a punk band, their concerts becoming successful with him screaming in a unique way. Must be a film from the 90s, not sure if a TV or cinema production, could be Australian? I guess it's an independent production, also the actors aren't famous. Thanks!