What does it mean that you knew someone that did this? It means your brain is not fully functional, if you continue to believe that it is a good thing for guns to be freely available and commonplace.
My brain is quite functional, and not once have I said I think firearms should be freely available and commonplace. You are merely automatically placing me in the 'raving pro-gun lunatic' band because I happen to shoot.
As a matter of fact, I believe there should be tighter restrictions on air weapons. I don't, however, believe that those of us rational, responsible, and skilled enough to own and operate firearms should be unable to access the firearms we desire for reasonable use.
You can go and buy a stupidly powerful car, drive it like an idiot, and kill someone. People do that every day. But I can't go buy an AS50 and place holes in a piece of paper from 1500m away in a safe, controlled manner.
I know, next time someone drives into a bus and kills a load of children on their way to a field trip, we'll ban all cars except Kei cars.