Justin, while the concept of a gun free society has its attraction from a safety standpoint, you are a bit too late. If you could go back 240 years and convince our founding fathers that an armed citizenry was a bad idea you might get your wish, but having just won their liberty because of armed citizens I suspect you would have a hard time of it.
In any case, we have been an armed society for centuries now and there are currently over 300 million guns in circulation in the USA, many if not most of which are semi-automatics. Concepts are easy, but practical solutions are not. Since laws only affect law abiding citizens, attempts at banning firearms will only swing the balance of power to the non law abiding criminals, gangs, drug addicts, terrorists, fanatics, and sick people. If you can figure out a way to take all of their guns away first, I might let you have mine, but somehow I don't see them lining up at the local police station to turn in their already illegal weapons. Until then I need my guns to protect my family from them, and semi-automatics are the best protection, especially from multiple bad guys.
It is unfortunate that some people abuse their right to self-protection with firearms and hurt others, but that is not unique to guns. Banning the tool is the wrong approach. Steps in the right direction might be more efficient detection of twisted minds, better enforcement of existing laws and tougher sentences to keep people who use guns in crimes off the street. Wish I had a cleaner, simpler, easier solution, but this is a complex problem that doesn't lend itself to knee-jerk emotional reactions.