Why is a pressure-cooker bomb a "weapon of mass destruction" but

[Xithras]

17. WMD has a specific definition.

It's a device that is capable of injuring or killing multiple people with a "single action". Set a bomb off once, it kills many people. A gun is only designed to kill a single target per shot.

Firearms are certainly destructive devices, but they fail the "mass" test because they require multiple actions to achieve their destruction against multiple targets. If you could design a single bullet that, when fired, would steer itself around a room to kill everyone in it, that would be a WMD.

The real difference is selectivity. With a firearm, every death is individual. The shooter chooses a target, points the weapon at them, activates the weapon, and then repeats the process again for the next target. Every person shot in a mass shooting is shot because the shooter specifically targeted them with their weapon and pulled the trigger.

There's a pretty simple contrast between that and a WMD, which simply targets everyone indiscriminately if they're in range. Instead of choosing to kill individuals, they are choosing to kill EVERYONE.