IIRC, the round was designed primarily to provide a side arm sized weapon capable of defeating body armor...even though it's a relatively puny pill coming out of the muzzle, I'd imagine its velocity at close ranges produces a formidable degree of hydrostatic shock, and would quite literally allow you to shoot into a crowd of people and wound several with each round due to its inherent penetration.
That would be 5.7 mm not caliber.
I had thought they might have made that mistake as well. But the last I heard the FN Five-Seven was not available for civilian purchase.
I think that it is a surprising choice. A .22 cal handgun? It indicates to me that this was a well planned terrorist attack. If someone just “cracked” why would they be using a specialty gun designed to penetrate body armor?
Ammunition
Particularly significant to the design of the Five-Seven is the 5.7x28mm cartridge created by FN for use in it. This cartridge weighs roughly half as much as a typical 9x19mm Parabellum cartridge[19][20], allowing extra ammunition to be carried more easily. It also produces roughly 30% less recoil[16][20], improving controllability.
One of the design intents of the SS190 variant of this cartridge (not sporting variants) was that it have the ability to penetrate Kevlar protection vests such as the NATO CRISAT vest.[16] In testing conducted by Passaic County, New Jersey Sheriff’s Department, the SS190 penetrated 11 inches in bare ballistic gelatin, and penetrated 9 inches in gelatin protected with a Kevlar vest.[17] The SS190 and similar 5.7x28mm projectiles have been shown to yaw or “tumble” in testing in ballistic gelatin and other mediums[16][17][21], using the .850 inch projectile length[9] to create a larger wound cavity. However, some are skeptical of the bullet’s performance and question whether this behavior is sufficient to overcome the bullet’s small diameter.[16]
Since the SS190 projectile does not rely on fragmentation or the expansion of a hollow point, FN claims the cartridge (and the Five-Seven) are suitable for military use under the Hague Conventions of 1899 and 1907, which prohibit use of expanding or fragmenting bullets in warfare.