As police investigated, they wondered why nearby residents weren't reporting the shots. It turned out that, in an effort to conceal his murders, Dorner was using a silencer, which distorts the sound of gunfire and masks the muzzle flash of a gun. (Silencers do not completely silence gunfire, as some Hollywood movies would have you believe.) In expert hands, say SEAL Team Six, silencers have been used to help covertly take down the likes of Osama bin Laden. But in the hands of criminals, like Dorner, they pose a serious threat to law enforcement officers and the communities they serve.