A single person using a knife or cleaver could kill a few victims before being stopped. Someone armed with a gun or using a vehicle as a weapon could kill dozens. The use of improvised explosives packed into pressure cookers could theoretically kill hundreds, and if quantity was the objective, radioactive nuclear material or chemical agents could kill thousands. But depending on the delivery and dispersal characteristics of the payload, a genetically modified biological agent might be able to kill millions, even billions. The international community held fast to the belief that nobody in their right mind would ever use such a barbaric weapon; but not everybody was in their right mind.