Most of those cases were the result of people who had psychological problems of one sort or another. The weapon is in the mind of the perpetrator. It is simply the mechanism by which the evil do their deeds, and most of the guns in this country are owned by law abiding people who don't shoot other people.
Your arguments are wrong headed. We can lock up the crazies and keep a watchful eye on them, but we are not even trying to do that, and haven't for the past 30 years.
Gun laws only affect the people who obey laws, clearly the people who commit these kinds of crimes do not fit that profile.