Inevitably whenever a gun-related tragedy occurs, we are told that if we want to "ban" guns, we have to "ban" cars, kitchen knives, meat skewers, baseball bats, hockey sticks, shovels, rakes, andirons, flower pots, and anything else a person might pick up and use as a weapon. It seems almost absurd to have to explain the difference between guns and tools, between something that can only be used to kill, maim or threaten and things that can be and are typically used for other purposes. But there's more to it than that.
[BTW, just as an aside, I put "ban" in quotes for a reason. The word "ban" is often used in place of the word "control" by people on both sides of this issue. Just to simplify, the right accuses the left of wanting to ban guns, when in fact what most of us are talking about is controlling them. And there are also people on the left who use the word "control" as a euphemism for "ban," in order to seem less anti-gun. But that's a separate topic.]
What guns are mainly about is power. I'm not talking about firepower; I'm talking about how a person with a gun feels about being a person with a gun. Having a gun gives you power over others, particularly others without guns. Guns create a disparity in power between the armed assailant and his potential victim(s) that is not the case with other kinds of weapons.
Killing a person with a blade, a blunt object or one's bare hands is difficult, dangerous, slow, messy and very personal. The victim has some power in that scenario, even if it's less than that of the assailant, because the assailant has to put himself in immediate physical danger in order to carry out his intent to kill; there is risk involved, including that the victim will be able to overpower the assailant. A gun, however, takes all of that power away from the victim and vests it in the killer. With a gun, killing is quick, easy, clean and convenient; you can kill from a distance, indiscriminately, without (literally and proverbially) getting your hands dirty, and without taking any personal risks or putting yourself in any immediate danger.
Guns therefore give people power over others not because of what they can do, or what people can do with them, but because they virtually eliminate the risk of doing it. Guns make people feel powerful, because people with guns can threaten, harm or kill others without putting themselves in, or perceiving, any immediate danger.
[Of course there is legal risk involved; that's not the point. Assaulting another person always puts you at risk of criminal prosecution, no matter what weapon(s) you use. I'm talking about immediate, momentary, mainly physical, risk.]
Even if the potential victim(s) in these scenarios is/are themselves armed, the disparity in power still exists as long as the assailant has the gun in his hand, locked, loaded and ready to shoot, and the other guns are concealed, holstered and safetied. I only mention this because the obvious counter-argument here is that the assailant is taking a risk if his targets are themselves armed, therefore the solution is to increase the assailant's risk by arming everyone else, and thus equalize the balance of power discussed above. It's a dubious proposition. And beside the point.
People kill for a great many reasons. People kill with guns because guns give them more power over other people; they make killing easier, quicker, cleaner, less personal, and most importantly, less risky.