Any gun can be a cop killing gun.
THe significant thing abiout this gun is that the ammo was developed by FN for the FN 5.7 hand gun and the FN bull pup style full auto carbine.
Out of the FN pistol, this ammo reaches muzzle velocity between 1800 and 1900 fps, near rifle velocity.That is why only jhp ammo is available to civilians.The military ammo can pierce class II body armor.Military 5.7 x 28 mm ammo is not available to civilians.
This is not anymore a cop killing gun than any gun.But it has a 20 + 1 mag. Lots of shooting without recharging the gun, and the high velocity ammo would go through three bodies before exhausting itself, like a rifle.Hasan’s purchase looks premeditated.
IIRC, the 1800-1900 number is only with the P90, not the FiveSeveN.
Also, the overpenetration (and corresponding lack of bullet expansion) issue is what makes the FiveSeveN a terrible choice in an environment where people are not wearing armor - damn thing doesn’t do much permanent wound damage and just keeps going.
He would have done worse damage (and killed more people) if he’d had two run of the mill 9mms as IIRC nobody in the hall was wearing armor.