knife technology.

found this sketchy thing on gizmodo.

"British police are on the lookout for something called a WASP Knife, a weapon that injects a ball of compressed gas into its victim that then expands to the size of a basketball, instantly freezing and exploding their internal organs. The blade, which was designed to help hunters and divers bring down large wild animals quickly, could possibly be bought on the internet by serial killing-minded crooks. Look at what it does to a watermelon!"