Guns aren't the problem.
Nor the availability of weapons.
If someone wants to do something bad, then we have all seen that he can do this with cars, trucks, etc.
People have shown themselves to be kill even with trucks ramming people in the streets, as you said when a person conspires to do something evil there is little than can really stop the, from doing it. Guns is not the problem at all, wicked humans are the problem.