Guns are definitely a major problem - a lot of people who shouldn't have access to guns do and use them. I'm not talking about intentional, targeted murders or settling gang disputes - those will happen anyway regardless of the law.

However, easy access to guns mean that people in an unstable mental state might use one to commit (mass?) murder in an act of folly that they would otherwise not do (or at the very least significantly reduce the amount of victims if they had to use a knife instead of a ranged weapon).