Guns are designed to expel a projectile. Killing is a function of what that projectile hits, and that depends solely on the shooter.
I believe the original patent called a firearm “A machine for throwing balls.”
Lead balls.
Granted. They expel projectiles. The designers of the first and subsequent firearms were and are aware of the purposes that those projectiles are used. The first “hand cannons” were designed for war to eliminate the enemy.
There is nothing wrong with owning a device to protect oneself and if need be used to injure or kill someone as a means of protecting oneself.