A gas generator usable in a vehicle occupant protection system. The gas generator includes an initiator holder and an initiator secured within the holder, the initiator including a housing enclosing an initiator charge. A bore seal is molded into the initiator holder, and a casing is attached to the bore seal along an exterior surface of the bore seal. A gas generant material is positioned within the casing so as to enable fluid communication between the gas generant and combustion products formed by combustion of the initiator charge, thereby enabling ignition of the gas generant. In one embodiment, an edge portion of the casing is pre-formed so as to snap-fit over a shoulder formed along the bore seal. In another embodiment, an edge portion of the casing is crimped onto outer surfaces of the bore seal. In yet another embodiment, the casing is welded to the bore seal.