You are heavily underestimating how comparatively hard is to get any kind of gun here. Literally no one in my family and not one of my close friends and event my neighbors in my apartment block have access to ANY kind of gun. Sure there is possibility if You have lots of time and money and if you are relatively stable person to get a gun (I used to know a guy who was a member of shooting club and thus was able to buy himself a gun), but this process has so many hoops that it is actively discouraging from obtaining one just because you fancy one (as an impulse buy). And thus I believe that it makes it a lot harder for unstable people to get hands on them when they got the impuls to do some damage (I believe that planning and persistence required to get gun here is antithesis to what makes those people go on killing spree).
>> So when you say "they do not find a way to get the guns", you're suggesting that the potential mass murderers are out there, looking for a way, but failing to get the guns. But clearly they should be succeeding occasionally, the legal way. And yet we don't see it. Why not?]
I think that's because they are a lot persistent that You believe them to be. Emotions and planning do not go together well. And there is also social element here - You have to be in a sport club and be vouched by others to get to the guns. This two things put together seems to eliminate almost all individuals that would otherwise blow out tunneling their anger through guns.