Funny to see this debate on SS.
My opinion is that these guys who cause "mass shootings" (quotes because this typically is defined as 3-4 "victims" of gun violence which seems like a bit of a stretch) are going to inflict damage in any way that they can. Whether they use guns, knives, or a vehicle that they run into a big crowd of people, if they want to kill a lot of people they can in modern society. Unfortunately, with greater technology comes greater responsibility and greater risk.
Guns are easy from the standpoint that they typically are the least personal way of killing another human being. You pull the trigger and it is over. A knife requires close proximity; a car you will hear and feel the carnage. But the fact is if guns are outlawed, these other methods would start getting used by these psychos.