It's not guns - it's the bullets. The bullets propelled by gunpowder from the casing, ignited by the primer which is set off by a firing pin, released by a fire control group which is released by actuation of a trigger operated by a person - who is not controlled by anything.
And if that human didn't have a gun, he would use a knife, or a hammer, or poison, or fire, or...
People kill people.